I prefer the small simple helmets to the bulky over the top ones, I've always considered my potential spartan alter ego to be proficient in black ops infiltration missions meaning small light weight armor for speed and maneuverability. So I'd go with the air assault or the security for sure. I would always consider a pilots role so in Halo 4 I chose small torso with the rogue helmet (it just seems that a pilot would want maximum peripheral vision).