Well, it would certainly be between Ninjutsu and Taijutsu for me. Genjutsu would only take someone so far in a physical world, its a hit or miss type of weapon and its quite boring imo. For those reasons i wouldn't go with Genjutsu.
All in all i'd go with Ninjutsu. It offers much more possibilities and i could use it to make up for my lack of physical prowess anyway.