This reply confused me to a certain level... Honestly I'm not sure where you're talking about GregTech and where you're talking about EE. All I'll say is, GregTech takes longer and more effort to "exchange" items. Where EE does it instantly if you have the stone, and the stone is easy to get no matter how it's done. Whether it's a mob drop or requires you poisoning yourself. If it's poison, drink a regeneration potion. If it's mob drops, make a mob farm.
For GregTech, you take a stack of netherrack, stick it in a machine, wait a bit, pull it out, stick it in a workbench with flint, put it in another machine, then wait awhile.
The energy distribution is automatic. You dump a stack of coal (coke) in a generator. Boom. Done.
For EE3, you first need the minimum stone, which you have to craft, and it runs out. So you kill a bunch of mobs (in the current version). Not hard, but harder than throwing a stack of coal in a generator. Then, you stick cobble (which, if you're mining the normal way, is harder to get than netherrack, else it's the same) in a crafting table, make as much as you can, then go make another stone, which means farming more mobs. Meanwhile, the GregTech machine is still running, without you doing ANYTHING. Then, you have to manually craft all the various "tiers" of materials to work your way up to a single diamond. So let's count it in terms of interface interactions:
GregTech
1 (Dumping a stack of netherrack in the machine)
1 (Dumping coal in the generator)
1 (Grabbing stuff from the centrifuge. Can be automated, if you want)
1 (Crafting Table for coal ball)
1 (crafting Table for coal block)
1 (Compressor for block->diamond)
Total: 6, and a bit of waiting time, in which you can go do something productive.
Total Resources Used: 64 Netherrack, some coal.
EE3
1 (Minium Stone crafting)
16 (Cobble -> Wood. Assuming Shift+Click. 1024/1521 Transmutations used from the stone)
2 (Wood -> Obsidian, another 128 used from the stone. It's at 1152/1521)
1 (Obsidian-> Iron. 32 transmutations more. 1184/1521)
1 (Iron->Gold. 4 transmutes more. 1188/1521)
1( Gold -> Diamond 1 more transmute. 1189/1521)
Total: 22, and the need to go farm a bunch of mobs beforehand.
Total Resources Used: 8192 cobble (Same EMC as Netherrack, btw). Some sword durability (fighting mobs). 4 iron, 1 gold. Which, as you'll recall, is one fourth of the diamond to begin with.
Also correction to my previous post: The minium stone needs 8 shards of minium, 4 iron, 4 smooth stone, and 1 gold ingot for each one. So those are what you need to have before you start making diamonds.
So I say that GregTech is easier. On top of that, you can actually automate most of the process of GregTech's version, and you probably aren't even using just a regular generator for it, so you could possibly knock out the coal cost.
EDIT: By the way, I assume shift+click for any interface interaction, and I didn't include the act of putting things in the crafting table, because that would be the same for both mods. Also, you can use ACTs, redpower, and buildcraft to automate the GregTech version's process. If you want to do that for the EE version, you need to make TWO minium stones for EACH crafting recipe, because of the way AutoCrafting Tables work. And that would mean that you just spent more than a diamond's worth of materials to make a single diamond, so that's kind of silly.