Okay hear my list
Power characters: Lei Fang, Milla, Jann lee, Rig, and Hitomi
These ones are normally very easy to pick up and get a hang of cause there simple move list, easy combos and high damage from a single move.
Grabble characters: Lisa, Tina, Bass, Bayman
Grabs, grabs, grabs not much more. Average difficulty in learning if you good with memerizing moves in there grab combos.
Rounded: Kokoro, Gen Fu, Eliot, Pei, Ryu,
similar to power characters but require more practice to understand them since their move lists as some more punishment
Ninja: Hayabusa, hayate, Ayane, Kisume
The only reason they have their own list is cause each one is unique in themselfs. Though each one is pretty average to pick up (exclude Kasume) but each one is different in fighting and mastering.
Hard Mastering: Chirstie, Helena, Brad, Sarah
Not noob friendly! some of the longest and hardest combos. Easily punishable but worth it in the end.
But thats my opinion