If you are not sure if you are beating the person in front of you, but you are pretty sure you are beating the person behind you, you should just call on the river and hope the person behind you calls too.

In this spot, though, I would raise and call a reraise, because there are many hands the SB could have that you can beat and not too many that you can't.

No way I am folding for one more bet in this pot if the SB reraises me.