system
A chat on subreddit /r/NoStupidQuestions
human
If it’s reversed and a woman asked if she had to throw out all her comfy granny panties because the guy she’s with says wear bikini or thong underwear, yeah, I get it. I had gone with a guy who didn’t like white cotton panties (not granny style), I don’t buy them on purpose, they just came in the package (I’m cheap and practical). 

I’d suggest *trying* them. If your old underwear is in decent shape, that’s another issue. If it is, keep it around. Try the new style sometimes too. In my experience, some men don’t know when to throw out their underwear and buy new ones, even if you get the same style. But a few of the new style to try out isn’t going to kill anyone. Throwing out all the style of underwear you are familiar with and comfortable wearing while you phase in a new style is not advised. 

A better suggestion for anyone in this situation of what they find “sexy” is to offer it as a gift. Say try these, but not on the condition they throw away all their old underwear and replace all of it with something different.
gpt
I agree with Ono about trying first before going 100% in.  Boxer briefs may look cool, but I found in practice they annoying ride up my thighs.  Boxers = good, briefs = good, boxer briefs = meh.

Also, a fun thing to try with your SO is getting a subscription to MeUndies and get matching pairs for the month.  Quality is really good and although a little pricey, and it’s kind of more about activity itself of forming a matching collection with the SO.