Some character info:
Everybody gets to work from the same pool of def gear. Def gear is gained from kills / chests or from the store. Some stuff is female / male only, some stuff has slightly different properties for some characters.
Also note that if your health is full and you pick up an instant healing item (Tasty Meat, etc.), your health stat will permanently increase.
Alucard:
Can equip two weapons simultaneously or 2h weapons. Cannot equip guns.
Can use QCF+Attack to use special abilities from certain weapons.
Gains scrolls from kills / chests. Each scroll pickup increases spell strength.
Overall, the most basic character (so far).
Soma:
Can equip two weapons simultaneously or 2h weapons. Can equip guns.
Can use QCF+Attack to use special abilities from certain weapons.
Gains souls from kills. Can get souls from other player kills. Each soul pickup increases soul strength.
Is the only character (so far) who can change his RB assignment.
Jonathon:
Cannot equip any weapon other than the whip.
Gains new sub weapons and martial arts from kills / chests. Sub Weapon strength and overall offensive power (whip, martial arts) increases with sub weapon use.
Martial arts do not need to be "equipped", you can use them the second you get them (if you know the motions).
Charlotte:
Cannot equip any weapon other than the book.
Gains new spells by absorbing them with RB. Increase their power and overall offensive power (Book) by successive absorbs.
Only gets money and def gear from drops / kills, good for farming gold.
Is the only character (so far) who cannot dive kick.
Has the fastest (unassisted) magic regen.
Shanoa:
Gains ALL off gear (weapons and magic) by absorbing glyphs (hold UP when they appear). Increase their power and overall offensive power by successive absorbs.
Can use QCF+attack or alternate button presses to use special abilities / combos with certain glyphs.
Only gets money and def gear from drops / kills, good for farming gold.
Is the only character (so far) who can use magnets to get around (RB).
Thanks to thetrufenix at
http://www.gamefaqs.com/boards/997663-castlevania-harmony-of-despair/55887432