This is a tuff question for me, my Beatles tribute band gigs alot so we never "practice". When we add new tunes we work on them at home on our own and then try them out together at soundchecks 'til they're ready to play during a show.
If I'm working on a song for my original "band"(just me, playing everything, in my home studio) I usually have a specific bass sound in mind for a song so I will practice the song with that bass.
If you're talking about "noodling" at home, I use whatever bass I'm in the mood for/whatever's handy.