IMO Infinity is the best option if the server and everyone can handle the stress it puts on your computer. Otherwise, Etho's modpack or DW20 is probably also good. Etho's doesn't have Big Reactors, which is a pretty interesting way to go about things.
Here's a modlist comparison.
Fun facts:
All 4 modpacks (dw20, etho, infinity, dark trilogy) have the mods...
- AE2
- Bibliocraft
- either BoP or ExtraBiomesXL
- Buildcraft
- Carpenter's Blocks, Chisel
- Computercraft
- EnderIO
- Extra utilities
- Forestry
- either Funky Locomotion (3) or Remain In Motion (Dark Trilogy)
- IC2
- Iron Chests
- Journeymap
- Mantle
- Natura
- NEI
- Nuclear Control
- either Project Red or Blue Power, never both
- Thermal Foundation & Expansion
- Railcraft
- Steve's Carts and SFM
- Thaumcraft & tinkerer
- TiC & Mechworks
- Twilight Forest
- Wireless Redstone.
Etho's modpack has the most new/less well known mods, such as Archimedes Ships, Compact Machines, Custom NPCs, Deadly World, Rotarycraft (!), Galacticraft, Hardcore Ender Expansion, Mariculture (of Agrarian Skies fame, basically weaker bees), Mekanism, pistronics, Pneumaticraft, qCraft, spice of life. However, it's lacking a lot of comfort mods like Big Reactors, AOBD2 (which procedurally generatures dusts and fluids for IC2 and TiC), Aroma's backup, morpheus, Opis, BEES, etc. Also, there is no recipe tweaking since MineTweaker is absent.
DW20 also has its share of new mods alongside the familiar faces; it has less than Ethos but more than DT and FTB. It's the only modpack with Factorization. That said, it has basically the same mods as Dark Trilogy; I suspect that the DT modpack maker heavily drew inspiration from DW20. DW20 shares the degree of curation that DT has, with Minetweaked recipes and Dense Ores for fun little lucky strikes. DW20 and DT are both balanced for a relativly longer server life, while Ethos is not. DW20 and Ethos are also the two modpacks with PPneumaticraft and Mystcraft.
Everyone knows what's in DT, but some interesting facts are that it has the most addons--additional pipes, logistics pipes, extra cells, 3 Thaumcraft plugins, and the whole Bee set (magic, extra, and Gendustry).
FTB Infinity actually has a surprisingly few number of mods. I wouldn't recommend it anymore... of all mods to pick, it chooses Springboards. woo! It does have Witchery though, alside with DW20. It also has RFTools and Draconic Evolution, both rising stars in the modding area.
tldr: Ethos has a ton of new mods but the total # of mods is the lowest, and nothing is tweaked/balanced. Also lacks many old faces, making it very not kitchen sinky.
DW20 is DT's less hardcore brother.
DT "balances" stuff by making it harder, but has a solid lineup of mods and also arguably has the most content thanks to its rich addons.
Infinity strives to be something awesome but it's more or less a blend of dt and dw20.
In my opinion, (unless mcfry says that adding mods is too much of a pita) keeping Dark Trilogy with some minor config edits and script changes and some mods might be pretty ok. Candidates for new stuff would be
- rotarycraft and maybe reactorcraft or electricraft
- Witchery
- Archimedes ships!?
- Minechem?
- Mekanism?Even if you say no to editing the kod list, McFry, these two are serverside only and thus easier to do:
- Add a recipe for laser drills because why not
- Maybe unnerf plastic sheets?
Also, honorable mention to Flaxbeards Steampower. Item mortar is the best
edit: I personally kinda liked DT's steel progression, where getting your first 8 steel for a pulverizer and an induction smelter was a great achievement. However, I do not agree with plastic sheets needing 3 different metals, capacitors needing half a signalum bar, and IC2 MFEs being shoved into every redstone cell recipe, totally ruining the Leadstone->Hardened->Redstone->Resonant progression they had...
also, the angel ring recipe is genius.
Edit2: Infinity does have Thermal Dynamics! Their itemducts look just like Buildcraft's but function a lot better. However, compared to EnderIO (which sprung up to fill the hiatus between TE3 and Thermal Dynamics) the itemducts are just clunky. Meanwhile, the fluiducts and energy nodes have literally nothing they do better than EnderIO except the infinite energy conduit's capacity. Hmm.