But some will say the extra girth on a bass neck can slow you down a bit, especially on the fattest necks. Well, I wouldn't say slow you down so much as a skinny neck can allow you to play with more ease.
I have long skinny fingers and could play an Ibanez SR all day without fatigue. Just got my first Spector, a Rebop, which has a noticeably chunkier neck. It's still very comfortable, so not really an issue, BUT after playing an Ibanez for the last 4 years (and playing guitar for 20 years before that), I feel I have to stretch my fingers out a bit more than I used to.
Even my right hand is having a little trouble adjusting - the strings are spaced further apart so I have to compensate for that when I'm playing really fast (finger style, I don't use a pick). I figure it will just take a little getting used to and again, the Spector is extremely comfortable and I love it. I played a P bass ages ago that just felt l was playing an elephant leg!
So yeah, if you're going to use a bass neck as a weapon, or to hit a ball with, chunkier is probably better.
But seriously, I think it's more what you start out with or get used to. Some bassists can't stand Ibby pencil necks. As for me, I'm loving the Rebop and now have some serious gas for a U.S. bolt on. But I'd still play an Ibby and want one their Prestige models.