You can only have max 280HP bonus from Materia, after that all need to go to VIT.
Or that might be translation error.
I don't think that is the case, I was pretty sure you simply cannot gain bonus from more than 5 or 7 of the same materia, I can't really remember the number...
Don't think it's a hard cap on a specific stat, but type of materia, regardless of level. In which case, I'd go bloodthirst (HP) then lifethirst (HP/MP).