TBH, you find a pack to get you started, then after a while you start learning what you like and dislike within that pack, so you either look for another pack, or take the alternate route of building your own pack. All methods have pro's and cons.
For myself, I was Tekkit in 1.2.5, then heard about FTB, and started with Direwolf20 pack. Seemed to contain most of what I was used to, and some new stuff, plus a series to watch to learn the new stuff. Eventually I learnt what I liked/disliked, and none of the latest FTB packs matched my requirements, combined with the annoying update system that nukes your mod/config folder lead me to eventually take the plunge and work on my own pack.
FTB for me now is a great community, where you can actually talk with Devs and have semi-serious discussions. I feel that this community (players and devs combined) have helped shaped the development of many a mod.