My son has a NAPA creeper, pretty low and good for him. Will's only 5'8" and 170lbs though. My bud Tim had a MAC and he hated it, he was 6'2" and closer to 300lbs. I've never used a creeper, even when I worked in a repair shop. Grunt to the core.
Your being 6'6" and 270 probably makes it a bit difficult to find a lot of things. test drive a few before you buy.