If you are trying to play to the very edge of your abilities every time you play, either because your instrument is just really challenging to to play, or because you're playing really challenging material, I think focusing your practice on a single instrument makes sense. For example, probably 95% of my practice time for the last 8 or 10 years has been on upright since I suck at it and have been working hard to improve. Every time I practice, I hit the limits of my ability. Assuming that it was practical for me to have a lot of double basses at home, if I switched instruments it would be a disaster, because my double bass playing is intimately intertwined with the instrument I own, the dimensions, the little marks on the fingerboard that I use as position markers, the amount of rosin that I have on the strings, the action, the physical size of the body. The same goes for my bow.
The material that I practice on electric will feel somewhat different depending on what bass I play, but its not that common for me to play stuff on electric bass where I'm at the limit of my abilities. Not to say my abilities are outrageously high, its just that the gigs I play electric on, I'm not having to spend hours and hours practicing to be able to play that stuff. But a solo double bass piece I'm working on might take me months to learn because its hard and I'm still learning.
So I think you need to take Hubbard's comments in context. If I got the gig playing electric where the parts were just outrageously complicated, I would not fool around switching basses from song to song. But if I'm playing material where the sound of the instrument helps a song to sound better, and there are songs that call for different sounds, of course I'd take more than one instrument. I think that's what he's saying- if you're really hitting your limits, it helps to have one instrument that you really understand, but not every gig is like that.
The material that I practice on electric will feel somewhat different depending on what bass I play, but its not that common for me to play stuff on electric bass where I'm at the limit of my abilities. Not to say my abilities are outrageously high, its just that the gigs I play electric on, I'm not having to spend hours and hours practicing to be able to play that stuff. But a solo double bass piece I'm working on might take me months to learn because its hard and I'm still learning.
So I think you need to take Hubbard's comments in context. If I got the gig playing electric where the parts were just outrageously complicated, I would not fool around switching basses from song to song. But if I'm playing material where the sound of the instrument helps a song to sound better, and there are songs that call for different sounds, of course I'd take more than one instrument. I think that's what he's saying- if you're really hitting your limits, it helps to have one instrument that you really understand, but not every gig is like that.

