Flats are my preferred string, and I have a few different brands in rotation. I usually keep a bass with stainless rounds for that tone when needed. But since I'm not doing slap or hard rock or anything aggressive, I find myself using rounds less and less unless the project/song calls for it. Flats just sound right to me and support the band/sit in the mix so well and the bands I've been in often comment positively on the tone even though they don't know diddly about bass strings. So I'll really only use rounds when I have to. Even then, I keep rounds on for at least 4-6 months.
All this being said, my basses are active, so I can get a bit more versatility from them than on a passive bass.
All this being said, my basses are active, so I can get a bit more versatility from them than on a passive bass.