TBH, unless your hand is very small, probably becomes more an issue of like what I know, vs know what I like.
On a guitar, where the neck is all around larger, and it can affect if you can wrap your hand around, it might be more important.
But on a uke where the neck is still pretty small, I'm not sure it's as important.
Im not saying you wont have a preference, but I don't feel like it's so critical. Like.. a pono has a pretty thick neck, where the kala mass produced are thinish, but the kala slotted necks are thicker than the flat necks.
If you spend enough time to get to know an instrument, unless it prevents you from reaching something like.. thumbing g-string frets, Im not sure it matters so much.
If you watch the HMS vids, all the players play all the ukes... and make them all sound great.
now.. for full disclosure, I don't wrap my hand around. I mostly clamp the back with the thumb, and then press down on fret with the other 4 fingers, so my style of playing might bias my perspective differently from yours, which is why what I feel is thickness more than shape since my fretting hand doesn't reallly touch anything but the crown of the back and the fret board.