Are those keyblades not as powerful as the ones with the key chains? I hardly spotted any keyblades with key chains on them... except for the obvious one the old man was holding.
Also:
KHII:FM has additional cutscenes of story, additional enemies (like the Shadow Heartless Mushrooms from KH I FM) additional bosses (including one of the knights in the video, and the members of Organization XIII from Chain of Memories), additional costumes, and additional key chains for keyblades. There maybe more things... but all the ones I listed are really good bonuses... that and I think it comes packed with the PS2 remake of Chain of Memories.