To muddy the waters even further–I have a Gretsch Banjo that was my starter banjo a couple years ago. It’s got a standard flat fretboard. A little over a year ago, I had the good fortune to get permission from the boss to purchase a Nechville banjo. As many of you know, Tom Nechville makes his banjos standard with a compound radiused neck. So all of that is to say that I’m still a relative beginner, but have experience with both neck profiles. So take this for what it’s worth.
Honestly, I don’t feel significant difference between the two. Tom Nechville says that one of the main reasons he likes a radius in his necks is to provide added strength–which allows him to make a thinner neck. I love the feel of my Nechville, so the radius was important to allow the neck profile that felt right to me, not so much for the fretboard shape. The main difference when I’m playing is that I feel like I’m reaching into a valley when playing the middle strings on the Gretsch. The Nechville strings feel more readily available–and that is more due to the radiused bridge. So there you go.
I’'d also like to note that Nechville makes a “flux capacitor” that allows any standard banjo pot to be merged with his necks. So if you really love your current banjo and are driven to get a radiused neck, call the Nechville folks and ask about that. But it may be cheaper to have two banjos–your current banjo and another that is radiused.