Reasonably snug and so skintight so that you have to peel it off are not the same thing. It's counter-intuitive, but a well made base layer is cooler in the heat despite the extra layer. And I know we are in the same conditions.

Jerseys and base layer materials also are not constructed the same. My favorite used to be the Craft ProCool superlight mesh, but they don't seem to make the exact same model anymore. My current favorite is a Specialized "First Layer". When I wash it, I take it out of the washing machine and it is literally dry.

A base layer is also extra protection in a crash. It's not so much that there is more material, as that there are two layers to slide against each other. Let the friction be between the layers rather than your skin.