Both pretty much change the game and therefore should be treated as different games entirely.
That's exactly why I'm looking at modpacks. Ever since 1.3 and on, Minecraft has been feeling less and less like...well,
Minecraft, and for some reason bats, witches, and the new sounds mark the spot where Vanilla has jumped the shark for me. The modpacks give their own unique experience, one that's both cohesive and, importantly,
new to me, so I get that same thrill of achievement and the unknown as I used to with Vanilla.
So, question: Feed the Beast or Tekkit?
Well, all I know is in Tekkit you have the ability to create enormous and complicated machinery...
Yes, IndustrialCraft (I think, that or BuildCraft) is included with FTB as well as Tekkit (as are OptiFine and TooManyItems). (I should mention for the sake of fairness that I've played both Technic and Tekkit, but not FTB.) From what I've seen SO far, the big difference is that Tekkit comes with RedPower and EquivalentExchange2, whereas FTB has Forestry and the Portal Gun mod. I've never really used RedPower that much in Tekkit anyway, and EE2 is what sucked the fun out of Technic for me (well, that and the MASSIVE lag issues caused by Thaumcraft, which is a shame because it was actually my favorite part of the pack), so I'm hoping FTB will be more fun for me.