In all honesty, my quest for the perfect pants is not complete! But I've had varying degrees of success with a load of different stuff and have found that, unsurprisingly, the best choice from my selection depends on what I'm doing and in what conditions. And... (easily forgotten) what I'll be wearing with them.
These are what I've currently got 'in service':
Helly Hansen LIFA Dry briefs
Helly Hansen LIFA Dry wind briefs (as above but with a ?nylon? windproof layer over the important bits!)
Helly Hansen LIFA Dry boxers
Subzero Factor 1 briefs
Subzero All Active boxers
Patagonia Capilene boxers
My thoughts are subjective and have a lot to do with my rather burly Burley thighs - the result of years of rowing and a bit of a cheese abuse problem.
So.. the LIFA dry briefs are excellent for travel and as underwear for rock climbing, rowing and other non-impact sports. Easily washed/dried overnight as very fast drying. However, they don't protect from chafing and LIFA can be clammy in hot weather. Work well under leggings or lycra sports shorts.
LIFA wind briefs are an excellent invention IMO. They have the additional benefit over the standard LIFA briefs of being protective in cold weather and they also have more elasticity giving better support for impact sports. I use them a lot in winter for running, worn under a light pair of leggings, as they keep off the windchill and hold everything in place if you know what I mean. Sorry for that... but it's a selling point IMO. However, they are even more clammy in hot weather than the LIFA briefs as there's an extra layer of fabric.
LIFA boxers. These have the fabric advantages that I listed for the briefs and are a nice fit for me so are good for protecting from chafing for hiking & other day-long activities. Still a bit clammy in summer.
SZ briefs are made from Factor 1 nylon and it wicks extremely well. These are my warm weather sports underwear of choice for running/rowing/climbing in summer as they are more supportive than the HH LIFA brief without being constrictive and don't get clammy. However, I'm not sure they are sold anymore and I regret not buying more pairs when they were a fiver a pop.
SZ All Active boxers are an odd cut (although mine were from the sub standards clearout). I think the cut is standard however. Anyway, they are very stretchy with a significant lycra content and wick extremely well. They are firmly supportive which makes them good for sports and I like them a lot for rowing as they come up almost to the navel keeping my lower back warm when I'm bent over forwards. They're also good for protecting from chafing but the fit isn't perfect for me so I can get a bit 'tangled' in certain circumstances. Still, an excellent allrounder and no wonder that Bob at BPL stocks them.
Patagonia Capilene boxers are a more baggy style than the other two I've listed and the fabric is quite an open weave. They are great in hot weather and can help reduce chafing but aren't very supportive. Probably my first choice for summer walking.
I'll continue to try new things when I find them at bargain prices (none of the above cost me more than a fiver) but for now I've got solutions that aren't quite perfect...
John