I use both. Live, especially with a loud hard hitting drummer I use round wound strings. In the studio however, I always use flats. They record a nice fat signal & hardly need compression. I prefer black nylon tape-wound or nickel flats.
I have a 67 EB2, and I Always use the baritone switch. Mine is strung with black nylon tapewound
Strings. If you want the real 60 's sound, flat wound strings are essential.