In reply to Mattia:
The only merino bottoms I've used actively were a couple of pairs of Bergans (of Norway) and (as others have said) they were full of crotch-holes very quickly.
I use merino long-johns (Crane) and merino tops (Smart Wool) to sleep in and love them but it just doesn't stand up to active wear.
On the other hand, I have used Patagonia Capilene for tops and boxers over thousands of miles and they stand up very well.
In terms of warmth I didn't notice much difference. I use Capilene for active and Merino for sleeping because wool feels super comfy for low-output activity, where Capilene doesn't hold as much moisture (sweat or rain) and is robust. I also find merino a little bit itchy when sweating. The only downside with this system is that Capilene stinks where Merino doesn't smell with up to a week or more of wearing without washing.