I'm fairly new to MC, but ftb infinity seems to have it all: tech, magic, tons of useful little mods for every thing you can imagine. I've probably put 50+ hours into my infinity game and barely scratched the surface of the content in that modpack. It has been getting progressively laggier though as my base has gotten bigger and my tech tree has gotten farther. The first modpack I played was actually direwolf20, which is also very jam packed with magic and tech like infinity, you can't go wrong either I think, but I think infinity is slightly more jam packed with stuff than DW20. I've been trying out various modpacks and each one has it's own unique flavor and challenge, so you may just want to try out several of them including some of the third party packs like Obscurity, Blast Off, etc...I find some of them like Obscurity to be just too difficult and unforgiving for me to enjoy them. For example Obscurity...you start with 5 lives but one single creature sneaking up behind you or one ranged enemy early in the game can cause you to chain die easily because you start with one interdiction torch, and if you die and drop it far from the spawn....it's basically game over. You absolutely need it, but you'll lose all your other lives trying to get it back. And I've had to restart it about 5 times and the last attempt lasted like 15 minutes and it was game over again...But if you like a challenge then yeah play Obscurity or Agrarian Skies or Blast Off. Ftb Departed is also quite challenging in the early game. If your a big Lord of the Rings geek, try Tolkiencraft.