Don't forget that a player's preference in fingerboard radius also has a lot to do with the right hand. Maybe even more than the left hand. Back toward the bridge, a rounder (smaller radius) fingerboard raises up the middle strings and makes it easier to do more aggressive plucking. Back in the old days (like, the '60's) bass players plucked harder and didn't play as many notes. A 7 1/4" radius over the body felt more comfortable to pluck, if you are used to playing upright bass, and trying out this new-fangled electric Fender thing.
But bass playing technique has evolved over the decades. Modern players play with super low action and pluck with a light touch, using almost acoustic guitar finger-style right hand technique. Lots of fast notes. And then there's slap and pop technique. These players usually like flatter radius under the plucking hand, often even completely flat.
The manufacturers like Fender eventually started making their necks flatter, 9" and 12", because customers wanted them. It was more for right hand plucking technique than for left hand comfort. In the last 30 years, 12" radius seems to have become the standard for 4-string electric basses. It's a comfortable compromise between round and flat; both style players can be happy with it.
Left hand comfort plays a part too. And it depends on your playing technique. Players who use a lot of muscle will usually like a smaller, rounder neck. Light and fast, with lots of chordal work, you may prefer a wider, flatter neck.
The basses I build are mostly 7 1/4" radius, and I offer some models in 4" radius. They are designed for a specific market of players who do upright-style plucking.
These days, there is a lot of choice out there. Think about your right hand technique as you are trying out different basses.