I second local printers if available. It just makes shipping and sorting out issues easier.
Pretty much any print shop that has done magazines can do comics, at least from my experience looking at local printers.
If there are no local printers, the printers that specialize in comics all provide print samples which you can order and judge for yourself. I looked at Mixam, Print Ninja, and Ka-Blam before settling on a local shop. I think the Mixam sample looked the best out of the three but it's been a while.