Patroklos is a well rounded one because it gives you more diverse areas such a R.O , walls and breakable wall
DEV TEST
Ramus
TANHAUSSER1
Ely's stage is a good one to just go wild in, since it's like the Hyperbolic Time Chamber C:
CappuccinoJak
i prefer pyrrha's stage since it's a bit closed in so i can practice wall combos more reliably.
Der Lindwurm
I've always thought that practice is the only thing those infinite stages are good for.