Swimwear question...

Stop shuddering, all of you. The lycra's finally gone in my trusty swimmies. Now, there's no way on earth you'll get me in a pair of hideous grape-smugglers, but I'm torn between my trusty shorts and some longer jammers. Is the decision purely aesthetic (in a reduction-of-ocular-harm sort of way) or is there a purpose behind those long bike-short style legs? And why the hell are they called "jammers" anyway?

Also: I go to the swimwear site and click on the shorts, I get offered the shorts. I click on the sixpack, I don't get offered the killer abs. Wah! Call themselves slaves to my mad comsumer cravings?