The first Kingdom Hearts used MP when casting spells, which, of course, limited your abilities with it and also made more than a few people shirk away from the Mage class at the begining (it also doesn't help that it takes a very long time to get the good spells). Days had something similar where you could only stock a select amount of spells, and if you burned out, you were done. This limitation might hamper the hack-and-slash style of KH, but I think it had a lot going for it. For starters, it gives a reason for the items to exist. You would actually want to stock up on ethers and elixers because you were screwed if you needed to cast Cure and couldn't. It meant that the player had to plan their game better than just mowing through without a hitch. It made you play smarter, especially in Days: would you use you magic on the enemies you encounter at the begining, or would you save it incase is would help against stronger enemies later on?
Not to mention that the added difficulty with watching your MP bar did just that: it added difficulty. The recharging magic in KHII, as well as the Command Bar structure of BBS and DDD, makes it almost too easy. If you're being beat up on by a boss, you can just cast Cura, run in circles for a minute, then cast it again. This goes double in DDD where you can just spam Balloonra and napalm the hell out of enemies as you go on your merry way. It makes powerful magic become bogusly easy to cast and takes a huge chunk of the challenge out of the game.
The first Kingdom Hearts used MP when casting spells, which, of course, limited your abilities with it and also made more than a few people shirk away from the Mage class at the begining (it also doesn't help that it takes a very long time to get the good spells). Days had something similar where you could only stock a select amount of spells, and if you burned out, you were done. This limitation might hamper the hack-and-slash style of KH, but I think it had a lot going for it. For starters, it gives a reason for the items to exist. You would actually want to stock up on ethers and elixers because you were screwed if you needed to cast Cure and couldn't. It meant that the player had to plan their game better than just mowing through without a hitch. It made you play smarter, especially in Days: would you use you magic on the enemies you encounter at the begining, or would you save it incase is would help against stronger enemies later on?
Not to mention that the added difficulty with watching your MP bar did just that: it added difficulty. The recharging magic in KHII, as well as the Command Bar structure of BBS and DDD, makes it almost too easy. If you're being beat up on by a boss, you can just cast Cura, run in circles for a minute, then cast it again. This goes double in DDD where you can just spam Balloonra and napalm the hell out of enemies as you go on your merry way. It makes powerful magic become bogusly easy to cast and takes a huge chunk of the challenge out of the game.
So, for casting your magic: MP Bar or Recharge?