I generally use the Adidas compression boxer briefs, or a brand called Undertech that they sell at Meijer (for anyone in the midwest). Both have seams in useable places. Pumas were the only real no-go for me on a bike, their seams rubbed really bad in the saddle.
finally realized that if I was going to wash the underwear at the end of every day, I might as well just wash my padded bike shorts.
OTOH, I can carry a weeks worth of clean underwear in the space of a single pair of cycling shorts. Plus, I've never needed to bother with any sort of creams or butters wearing underwear. Double plus, if I want to change from cycling shorts to off-bike pants, it is much more appropriate to do so anywhere!