I've actually found that synthetic boxers cause me more chafing issues than merino or cotton ones. But generally for me I think it's as much about the moisture as the friction, and synthetics either don't wick away the moisture as well as cotton/merino, or they make me sweat more. So yeah, I don't bother with any sort of "athletic" underwear when running or hiking. Mountain biking I have a couple pairs of padded shorts. One is Icebreaker and work great, another came with a pair of Sombrio shorts and it's basically like taking sandpaper to my chodes. Something about the material covering the padding just destroyed my junk the last time I wore those ones.
Going back to the Saxx boxers, I picked up a pair of them and one of MyPackage, which is basically the same thing. They seem like pretty good quality boxers, but the "pocket" shit is pretty gimmicky IMO. I don't have a giant, floppy ball sack like a 70 year old man, so I don't really need the pocket. We'll see how long they last, which is the true test. Yeah you can get some super cheap Haines or Fruit of the Loom or whatever, but the best boxers I've owned have generally been Calvin Klein or Nautica. Super comfortable, and they last forever. On the flip side are merino ones by Icebreaker. Also super comfortable and great for hiking as they don't stink, but merino is just not a durable material. I picked up 4 pairs last year, and 2 of them are already done because of holes in the crotch, while I've got CK boxers that must be at least 3-4 years old that still look like new.