I havent ridden without pro team mesh for last 2k miles. Would reccomend, really versatile in terms of temp .. wicking in heat, an extra layer in slightly chilly. Merino mesh looks even better on paper; haven't tried.
Merino mesh is neither here nor there. I'd take pro team mesh for summer riding, wicks better. If you need the warmth of merino then you need a thicker base layer.
Rapha baselayers.
Mesh merino
Mesh pro team
Why one over other? I have the merino and like it, but wondered if the pro team would wick faster?
This isn't much detailed help.. http://pages.rapha.cc/products/autumn-and-winter-base-layer-guide