In the PS2 version, Alma's Trials aren't good for reaching high levels. You can choose experience as a reward, but the amount decays with your level, so at high levels you will only get 1 XP, which is much slower than just killing enemies for 1 XP each. Also, the trials are not repeatable.
Incidentally, Alma's Trials consist of lots of platforming, far more than you see otherwise in the game, and feature an orchestral soundtrack, in sharp contrast to the rest of the game.
With that said, the PS2 version does let you fight this boss in boss rush (at level 60), and there's a cheat in the PS2 version that lets you start the game at level 60.