I grew up wearing plain, white, cotton briefs (Fruit of the Loom or Hanes) as most boys did in the 70s and 80s.
When I went to college, I noticed that most of the other guys were wearing boxers--sometimes plain white, but more often with a colored pattern. Some of them would walk around the dorm in just their boxers. I certainly liked seeing other guys in their underwear, but I think there was a general consensus that a guy walking around in his "tighty whities" would have looked stupid. I liked the idea of underwear that could be worn casually in front of others, so I decided to try boxers. I enjoyed how "free" I felt wearing them. On hot days it was nice to get some air circulation. But they'd twist, turn, ride up, and need constant adjustment. My cock and/or balls were always falling out of the leg and/or the fly.
Then boxer briefs were invented. I tried them and had the same problem as thadjock--the legs would ride up. They also looked pretty strange. I couldn't decide if I liked them or not.
Over the past 2 decades, I've tried many different styles of boxers and boxer briefs. Most are uncomfortable for one reason or another, but over the years I've found myself leaning towards boxer briefs. I find that I usually feel like I need something with a little bit of support. Every morning when I'm getting dressed, I decide what I'm in the mood for. I may try on 2 or 3 different pairs to find something that feels right. Sometimes boxer briefs feel too constricting, and I choose boxers. Other times, I feel like I need support, and I choose boxer briefs.
Being rather frugal, I haven't purchased much premium underwear, except for what I can find at places like Marshall's and TJ Maxx. My current favorites are Merona and C9 boxer briefs, which can be purchased at Target.
A few years ago, after having not worn briefs for several years, I decided to try briefs again, and I bought several pairs in different styles. They were unwearable. I couldn't stuff myself into those damn things. There was room for my cock or my balls, but not both--and my endowment is average! I figured they'd only fit in one of two ways: 1) shove my balls up my asshole or 2) cut my dick off. I can't imagine anyone fitting into a pair of briefs, especially a guy who is well-hung.
Plug_It_In has a thread in which he reviews many different styles of underwear. I think they're all--or almost all--boxer briefs. I need to buy some new underwear, so sometime in the near future I'm going to re-read this thread and try a few of the pairs he recommends.
http://www.lpsg.org/90199-underwear-sale.html