Agreed, unless SB is nuts, best case is a coinflip. And even then, solid AK play is to go all in. I've never had the fortitude to fold in this situation, but I've wished I had many many times.

Edit: Oh yeah, why are you just calling UTG here? This actually makes SB's play not so strong. He could even be trying a Harrington squeeze play here. I was thinking you raised some reasonable amount.