RS5s - upper or lower connections?

Just bought a new set of RS5s. So far quite happy w/ the sound. But I'm curious: there are 2 inputs on each speaker (with a bridge), for bi-amping. I'm not bi-amping at this point, so I wonder which input to use, the upper or the lower. The manual says either is fine, and perhaps it makes no difference. But some say it does make a difference, and some even say you could connect one wire to the upper and one to the lower input. What do people think?

Thanks in advance.