I've got a question about underwear for a big guy...

So let's say I'm a 460lb guy who has just started walking for exercise. Normally I wear boxer briefs (best of both worlds amirite?). When I'm out walking it seems like they want to ride up a bit which makes everything more uncomfortable. I'm wondering if a pair of briefs or regular boxers would be a better option or do I just need to get a better boxer brief?

Any thoughts? Anyone with previous experience I can learn from?