Souldiers is a Western-hemisphere magical girl fiction story I read on a whim a couple of years ago when I needed a palate cleanser "fluff" book. The premise and all was pretty ridiculous (but what magical girls premise isn't?) but I thought the action scenes were pretty nifty.
Pretty disappointed so far with the tracklist in Project Diva X. I like the addition of medleys, but the 15 main tracks I have access to so far are all Miku songs (as far as I can tell, the game doesn't actually make that abundantly clear) and only 3 of them have genuinely caught my attention. Sure, some of them could grow on me, but compared to Project Mirai DX where I'm hard pressed to think of a track I didn't instantly fall in love with it's a let down.
I also kind of miss the Sim Vocaloid portions of the series. I felt they took it a bit too far in Project Mirai, but they've dialed it back so much it might as well not even be there (okay, mostly I just miss decorating the various rooms differently for each Vocaloid)
The one thing I do like that others might not be a fan of is the replacement of the usual item shop with a gacha-style reward system at the end of each song where you're rewarded a module and some items depending on your performance.
I feel like the Sound Design of VC really stands out in battle, with a lot of background sound happening that you don't necessarily notice but completely sucks you in. I personally am a big fan of the context-sensitive radio chatter, where you hear both your own army and the enemy's.
The slowdown is noticeable, but it's not enough to make the game unplayable by any means. I do feel like CSII runs a bit worse than CSI on Vita, though. It's prone to having many more characters on-screen at once and the engine rather obviously taxes the Vita's CPU.
Don't let that stop you from getting the Vita version if portability is paramount for you-- it's the same great game, after all! :)