I like a nice big handful (deep front-to-back), soft edges, 1 7/8" at the nut and 17-18mm spacing at the bridge, soft V or C shape, well-placed volute at the headstock, large treble side cutaway and smooth heel for upper-fret access, rock-solid stability, and even sustain and tonal response all the way across the fingerboard. 9 to 12" compound fb radius, or vintage Fender.
Dislikes: "U-shape" neck profiles with square corners and flat backs, super-wide fingerboards like some of the Squire V's, and extremes in trying to create a "faster" neck profile, whether it's super thin or super narrow. Dead spots and wolf notes. Flexible noodle-necks that offer poor sustain and/or tuning stability. Near-flat, 15 or 16" fb radius. Related issues: excessive overall weight that stresses my back and shoulders, poorly-placed strap attachments or body shapes that promote neck dive whether seated or standing, headless basses that don't provide a reference point for the first position.
Current favourites: The neck on the self-made 5-string in my Avatar, because it's been in my hand non-stop for the last 19 years, late 2000's Indonesian Ibanez ATK300's.
Promising future favourite: My still-on-order Dingwall ABZ-5. I tried a Combustion, and while I loved the fanned frets and fatness of the neck, it felt just a little "clubby" to me. I'm hoping that the slightly thinner ABZ profile will hit my sweet spot. Might even replace my number one!