I'm trying to decide between these or the x-temp version with mesh. Can anyone tell me if the mesh version is comfortable?

I don't know what this guy with the BS marketing for cotton briefs remark was talking about, especially since the x-temps are cotton-free. They are 92% polyester and 8% Spandex. The waistband on the x-temps is very tight and not the same as their regular Comfort Flex waistbands. And the x temps do not stretch out over time, much as I needed them to. I've been buying their regular boxer briefs in XXL, but they get too stretched out too quickly so I'm going with XL in the future. However, XXL in the x temps were ridiculously tight in the waistband - more like a Large then even an XL, and sure as heck not XXL! And as I said they don't loosen up with time. The fabric of them fit firmly but comfortably, and they are almost slippery to the touch. The whole Total Support pouch thing - not really sold on it. If you want total support you'll need a jock strap, unfortunately. And the x temps will have your butt cheeks sweating at times, especially on any hard seats, because polyester breaths about as well as a plastic bag. :/ I have not tried these other total support ones yet, but that's why I'm here too. Since they are a different fabric mix than the x temps, I guess I'll give em a shot, but I'm worried about which type of waistbands they use. I can't really decide which size to buy until I get that figured out. :/

My waist size is 35", in between M and L, which size should I buy?

They are true to size so I would go with a L for a 35 waist unless you like them a little snugger

How do i pick the size?

There was a size selection within the product on screen display but I've forgotten just where. If there had been no size option I wouldn't have ordered