My banjo (and all banjos I've owned) doesn't have a radiused fingerboard, but I have played a number of banjos which do. It's hard to make a comparison that I could really believe in, as there are a number of variables. The biggest is what the tonal difference would be. Since the neck mass and the action changes, that can affect tone. Hearing what someone else's banjo sounds like is not the same as hearing what my banjo would sound like with the radiused fingerboard. Unlike most setup experiments, this one would not be so easy to undo and redo a few times to check the effect. It would need to be played on stage as well as off, alone and in a group, etc. to make a good comparison.
Comfort-wise, radiused fingerboards feel fine, but I'm not really tempted to switch, as I'm satisfied with my banjo the way it is, and I do suspect it would change the tone.
Since you're thinking of a new banjo, it would be best if you could compare two similar banjos of the same brand, one with the radiused fingerboard, one without.