I wonder how it looks by your preference 
I didn't mind the old system at all, where we had differing energy loss per cable length dependant on cable type. It always sucked when you lost a certain amount out of transmitting power from for example a reactor to a factory, but I could (kinda) deal with it when I looked at it in percentage losses per EU/t generated. My only gripe with it was having to, for factory-type setups, transforming power down or up in order to use tin cable (which then also slowed down the EU transfer rate) for greater efficiency, but I guess that's the trade off; do you transform down, cut your power transmission rate and transmit more efficiently, or do you keep a high transfer rate and eat the losses.
The only real problem (and at the point I describe it should be just a slight irritation) I see is that you have to have a Tier 3/4 processing setup being fed somewhere on the underside of 70EU/t (think it's 69EU/t for all 4 machines?) as a minimum currently to have them running continuously which requires using copper cable to transfer as tin won't transfer that much power. If they're grouped (and you're using ejector upgrades to push relevant outputs to the next machine), it also requires transformers or transformer upgrades on all the machines bar the centrifuge (unless there's an item that I haven't heard about that lets you separate adjacent wire connections?). If you have your storage unit close enough to the machines then I guess it's not that much of a problem (as always with IC2, Prior Planning Prevents Poor Performance), but I could see it being an irritation to a lot of less thorough people (mind you these mechanics I've described are not new, so it's likely those that are annoyed by them have already moved on to other tech packs).
TL;DR: while I have my annoyances with it, I liked the old system, I don't think it needs to change much. Do think we could use some sort of item to separate adjacent wires though (since any wire placed adjacent to another will always connect no matter what).
I was actually thinking of energy tiers like cable conductor has main influence on cable losses...
That's an interesting idea actually; so we have the large majority of the resistance/loss from cables being based on their metal type, which is then fortified by their insulation/covering? Seems like an interesting mechanic, but I don't know how complex that is to do in Java, and there's likely a large priority list before any kind of power transmission revamp at present.
Not sure what you mean when you describe the function of dense or 4x cabling though; you say the packet sizes stay the same (Ok, fair enough), but it allows for a transmission rate four times that of regular cable? That I can get behind, but I don't know whether that might be imbalanced or not. I mean, you get the same EU/t transmission from the next 'level' of material, but it might allow larger packets or have less loss in transmission.
in lossy order [most lossy] iron->tin ->bronze->gold->copper->silver->graphene[almost losless]
Concerning your material resistivity flow chart, I see nothing wrong from a real-world-translating-to-minecraft point of view; however in terms of gameplay, I'd change a few things;
1) Either move bronze up to be better than both tin and copper or scrap it completely. I don't see anyone putting the effort in to make bronze cabling if they can just extrude copper (or tin, if it were better) instead; less effort, better results, and I'd say wasted programming time coding an item I foresee few people using.
2) Maybe keep gold above copper in terms of conductivity; it doesn't make sense from a real world standpoint (which probably makes all the Power Engineers that play this mod and others with similar transmission systems somewhat irate [IT MAKEZ NO SENZE]), but similar to the current system, gold is (at least before you obtain an advanced miner) slightly rarer than the other metals; thus making its use more valuable if it can transmit more power, or have more conductivity than other more common metals (I'd say iron is the exception to this only because you use so much of it to make other machinery anyway, to then have to use more ingots as cabling is just a kick in the nuts. At least before you obtain an Advanced Miner).
3) I'd be tempted to say take silver out, if only because IC2x (on it's own) doesn't have silver ore as part of its worldgen (making it a rare, end-game (mid-game?) resource), but I'm pretty sure myself and others that play without a mod that worldgens Silver Ore are in the minority. Leaving it in, I'm also seeing silver as a 'cheaper' alternative to graphene, assuming graphene is made as hard to make as Glass Fibre is now; if it's just basically a type of coal dust wire then that may end up being easier to make, at which point silver cable runs into the same problem as bronze (more productive to make the next level of cable).
I also like the idea of being able to colour the cabling, but only in that it would seperate different lines by colour. I find playing AE2 that it's often easier to separate sub-networks via adding quartz fibre between cables then colouring it instead, but it's two different ways to the same solution; I don't need to differentiate the networks visually, I just need to separate shortest paths for channels. My personal preference is still for example using the wrench to enable/disable cable connections on a side, but honestly if the painted cable was implemented I don't think I'd complain (only when I have to colour a line last-minute because my planned layout didn't take into account adjacent cabling :P), but I think it would be wasteful coding if they implemented both for the sake of community happiness (assuming more people want one or the other).
I could probably cope with any of these, provided I started a new game with the updated energy net, or at least took some time to adjust/upgrade my cables and machines before updating IC2. However, there are some things that would be nice to have to go with any of them:
1. ability to add transformer upgrades to all electricity-accepting machines - even if the "lossless" option wins, I expect machines would still have default limits to how much EU/t they could take without exploding.
2. a way to numerically show the current EU buffer level and input allowed for machines (possibly as tooltips), considering the upgrades they have installed.
3. one or more cable types that allow more than 8192 EU/t, for the sake of the most power-hungry machines, such as a mass fabricator, a heavily overclocked thermal centrifuge, or a molecular transformer (from the advanced solar panels mod)
The only real problem (and at the point I describe it should be just a slight irritation) I see is that you have to have a Tier 3/4 processing setup being fed somewhere on the underside of 70EU/t (think it's 69EU/t for all 4 machines?) as a minimum currently to have them running continuously which requires using copper cable to transfer as tin won't transfer that much power.
Why would you ever use tin cable instead of copper, which is much more common? Save your tin for burning in nukes.
I was actually thinking of energy tiers like cable conductor has main influence on cable losses - so
This is how it used to work. I'm glad they got rid of it since in real life insulation has nothing to do with loss and is only there to prevent the electricity from leaving the cable and going into something you don't want, like your body.
I personally like the IC2 (1.4.7 or lower) power at the most.
True powerloss was a little bit a pain but with good combinations i was able to everything i wanted without much powerloss. Note for it that Tin And Silver(IC2 Glass) cable had the same amount of powerloss.
And powerloss is usefull. Sounds not right?
Simply the really cool thing about IC2 was that it damaged entities.
And there was powerloss usefull because you had to keep up with the cable power loss. Else it were a to op way to kill Entities.
Note that the damage was so extreme that you even if you weared 3 parts (body was a jetpack) of Quantum suit were not able to keep up with the damage you gained over Time^^"
If we talk about 2048 EU.
Also a note: You were in ic2 able to change the powerloss with rubber 
not extreme but a little bit.
So it seems that most of you would like to see real life energy net ;)still all current would be just AC with frequency hidden, and presented voltage would be "effective" voltage.. but le it be - i'm now coding e'net so i'll include option to make it realistic. I hope full cpu core to energy mesh and whole calculation stuff should be sufficient even with realistic model
Look into IC2 1.4.7 Source how they did it.
Because cables do not effect the Tickrate of the game.
The wires simply do not tick and are only paths
That makes the game easier and reduces the lag if you do not have 2M (2Million) Powersources that send energy.
that is exactly as i'm coding it right now 
I do not like idea of realistic e-net but creating it as option is realy nice idea if someone want more complex gameplay
I like ideas for precentage and per cable
I would really like to have lossless *short* cable runs (the way copper used to work), because loss every meter is leading to some hella awful design. But I like the idea that all longer runs involve some losses, with uptransforming to reduce them.
