Cross Edge?
That's the only game I've ever platinumed twice - on 2 separate PSN accounts
IMO, the 'hardest' & most time consuming part of Cross Edge, is that *Huge* initial learning curve / difficulty spike that is learning, getting used to & comfortable with, and remembering how all of the many different systems + gameplay mechanics work.
It's A LOT to take in.
It seems (initially) overwhelming & intimidating; seriously - it's the 1st & only game that I've ever felt like I had to "study" (ie: read & re-read) so much about it, until it finally all clicked.
Having played & platinumed both Cross Edge & Tears to Tiara 2 + knowing a bit about the games that you (we) like, I'll give ya some considerations to help you decide
Tears to Tiara 2 - Much better story & OST
Cross Edge - IMO, the best & deepest combo/combat system to ever grace a RPG
- You'll like & get a kick out of all of the playable N1 (and more) characters, like:
Etna & Prinny from Disgaea,
Morrigan, Lilith, Felicia, Demitri, and Jedah from Darkstalkers,
Shurelia, Misha, Aurica, and Lyner from the 1st Ar tonelico game,
Lily, Whim, and Raze from Mana Khemia 2,
Meu & Zelos from Spectral Souls, and probably another 10 or so exclusive to Cross Edge.
Platinum-wise = I could *easily* plat Cross Edge...twice, in the same amount of time that it'd take to plat Tears to Tiara...once