I can't speak to anything Scubapro, but the Calypso is a surprisingly good value even though it is an entry level unbalanced piston. I should qualify that I am speaking of the current version - if you are looking at something used, then that name has been used on various iterations over time that are not all "created equal."
The Calypso WOB (work if breathing) is 1.0 joules/liter, which is really pretty good. Better yet, that is tested at somewhat extreme conditions of 165 ft and 725 psi, so the fact it is unbalanced doesn't mean it will noticeably affect performance.
It is also cold water rated per EU testing standards, even though Aqualung does market it as a cold water regulator. What more could you want for a $300 set? Just be sure to get the Calypso/Titan octo too, and not an ABS octo that is not suitable for cold water.