GT from Ultimate and GT5 are completely different monsters. GT5 is far far far more intrusive with regards to both vanilla mechanics, world oregen, and technology progression than Ultimate ever was.
Pretty much any other techmod falls into the mid-game GT techtree, so without the hardmode recipes from GT, or some heavy recipe editing, mods like TE or EIO can completely break GT5's progression making most machines from GT up to MV electrical era useless.
GT Ultimate from what I recall just added more endgame to IC2, now GT5 is pretty much it's entire own mod which overlaps IC2 in a lot of ways, and is more akin to an overhaul mod ala terrafirmacraft, than a stand alone mode like EIO.
It's not for everyone, but GT5 is really rewarding when played the way it was intended. Beyond Reality as stated does a great job of balancing some of the fun and convenient mods around the GT progression tree. From what I've read Resurrection just added in GT for nostalgia's sake really, with little balancing or buffing of GT's or other mods difficulties to make them on them more coherent.