From what we've seen, it looks like Valor/Brave Form will be the most commonly used transformation drive. I'm not a fan of magic, so the blue form probably wouldn't interest me.
I'm personally hoping for a transformation drive with an absurdly long reach (similar to God of War's Kratos' primary weapons), or a drive with a two-handed sword or a decently long staff/spear. It's not likely to happen since the Keyblade is a single-handed sword, but... I can hope, I suppose.