I'm getting a Squier Fretless Vintage Modified J-Bass, so I can switch and getting into some more interesting bass playing. I want you get your opinion on the following question: As far as tone, what is the difference between fretless and fretted? Which one is warmer, brighter, darker, etc.? Help me out UG.
Fretless guitars generally sound warmer.
There is no inherent difference other than that you're not going to get a metallic clank by hitting the frets whilst playing a fretless if you dig in. Fretless is often described as sounding darker, but that isn't the case, rather there's a tendency towards flatwound strings because they're more friendly to fretless boards. If you use roundwounds on a fretless it's no warmer than a fretted bass. The "mwah" sound you can get on a fretless is something you obviously won't get on a fretted bass.
The metallic clank is what makes a fretted bass have a brighter attack, giving a perceived brighter sound.