If we're going for quantity and stuff, it's probably 1.7.10. That or 1.2.5, because back then, adventure style modding was HUGE. (New weapons, armors, mobs, simple stuff you don't see in FTB much :u)
Quality/modpacks is between 1.10 and 1.7.10. FTB Unstable 1.10 has a lot of fun mods (Psi), but it doesn't have all the tech stuff (and Thaumcraft) that most 1.7.10 packs have.
