What I like about Arg:
Very unique character that rounds out the initial cast well and has really great flavor. Moves that do no direct damage but are still really useful (Pacifism)! Overlal defensive moves. Poison that is easy to activate and lets him win with indirect damage and keep away, creating a tense little "mini-game"
One of the characters that feels most like their Yomi "counterpart", probably especially after Bubble Shield is added (read its description in the move list and it seems cool)