For me rounds are the thing, but finding the right set took quite a lot of time.
1) The right one here means that I use two brands, but similar gauge sets (SS RW) in every bass I have.
2) This helps to carry an extra set in a bass case, because that one suits, yes, every bass.
3) It's cheaper to order 10 sets at one time than 1 set 10 times.
4) The feel is nearly the same through all instruments, although scale lengths (33.8 - 36") have some effect on it.
Maybe I am a fanboi of the string sets I use now, but there was a long and pricey trial and error period. Someone asks why I do not list the sets? Only because I believe that everyone should test different sets and find the right types, brands, and gauges that go together with the instruments and playing styles people have. My choice most probably isn't suitable for you.
How I see strings:
- tapewound: short sustain, lousy sound (which isn't automatically a bad one)
- flatwound: a bit more of everything to TWs
- groundwound: see previous
Every set mentioned so far can be held in a bass until a fret cuts the surface of the string.
- Ni RW: flat, pretty full response, good for rock, and fretless
- SS RW: enhances highs and lows, thin sets can be really twangy (Miller and King obviously change their strings after few hours of playing)
Specialities like a piccolo set can be fun for some time.