Neck Thickness

I've played ukulele since about 1966 and I can say that based on my many decades of ukulele playing, it is the width of the neck and string spacing that makes far more difference than the thickness of the neck. Thickness can be comfortable with a rounded or "C" shaped neck. It can be comfortable with a flatter or "D" shaped neck. I've even played "V" shaped necks. A lot depends on how long your fingers are. But, the key to all of this is the balance of the instrument and are you a finger-picker or do you primarily strum the instrument? Believe it or not, you adapt pretty fast to new neck configurations when you play a lot of instruments.