I go thumbless simply because its more comfortable. Off course you can't be effective in the deadlift with a thumbless grip. I'm a powerlifter. But most big benchers, and when I say big I mean 7 hundred plus, they all say never use a thumbless grip because you risk losing the weight. If you've ever seen someone lose the weight while benching, you'd switch to a thumb in bench...QUICK!! LOL! I've tried it but because both my thumbs are distended from multiple dislocations, its simply more comfortable for me to go thumbless.