I prefer not to "dump" logs directly in php as especially in PHP code this quite often leads to an output in a browser which some people take to production.

The curl implementation has a specific reason. It makes it really simple to debug some queries that failed by just copy-pasting it into the console.

I agree that it is the responsibility of the Request and not Log to know, what the string looks like. But the current implementation (as before) is really focused on Http transport (which is the one the is mostly used). So I'm ok with this at the moment, but in case I have a good idea, I will probably refactor it. 

Probably also the symfony plugin guys will think about how this log stuff could be logged into the symfony debug window.