chaos444 saidi'm a swimmer and i wear a jammer, never a fan of briefs.
I'm also a swimmer, I use a drag mesh suit to train with but when I compete I more than likely use a jammer.
Use a jammer because it helps to compress more area than a briefs would which can result in a slightly faster time.
Be careful when it comes to jammers, if you pick a full body suit, try to stay away from events that last longer than 200 yrd or 200 meters, you run a greater risk of over heating.
Over all remember to take care of your suite...I had a TYR lazer..it lasted me for 12 meets...remember to wast in cold water...keeps from falling apart.