You playing on just a PSP or do you wanna play on your TV with a PS3? Far as I know, DXC still doesn't have Vita/PS TV support and would be confined to a PSP.
Also, while SOTN in DXC (an unlockable along with Rondo of Blood) has some extra goodies and things originally omitted from the English release, its image quality is a bit filtered and doesn't look as crisp and grand as the PlayStation version. I'd recommend getting the PS1 version of the game on PSN if you want the best video quality and to play on a TV.
If you're just playing on a PSP, though, then just go with DXC and read up how to unlock SOTN (and Rondo).