I kind of have my own style. I like castles and such, but I also like brighter colors and designs. And it's not really like the usual modern houses you see in Minecraft. Those modern houses look really 60's style, which I don't really like So I have my own unique style that I developed during my time building based off of colors/designs I like.
I like to build medieval-ish exteriors, mostly out of spruce and stones. Inside, I like to use really bright colours and quartz (or just white wool, if quartz starts to look funny). So I guess you could say both.
I'd say I build a sort of hybrid. What I mean by this is I build sort of rustic homes and such but with some modern details. I also don't exactly build "medieval" style stuff, like castles and fortresses.
I build mainly medieval stuff, pretty much anything but modern though. It just seems like minecraft wasn't designed for modern builds because the average modern house looks dull if you try to go for a realistic approach, and too make it look nice I always feel like I'm going over the top trying to make it modern. But besides medieval, steampunk is a lot of fun, and so is industrial aged builds.
I'm mostly medieval, but sometimes I do modern things. Like right now I'm doing a giant mansion. I don't know if you would classify me as medieval, though. I like doing old fashioned, but I sometimes also like doing fantasy looking things that couldn't exist.