Chad
Slender Hobbit
Honestly, I don't think that either one should matter, provided that healthy technique is there.
Exhibit A:
I think that this forum, as a collective, spends way too much time thinking about this kind of stuff. I don't know, maybe it's a guitar thing. We wouldn't be having this conversation if we were talking about an adult with small hands taking up the piano, or a child taking up a contrabassoon.
Your hands are amazing things, and they stretch and make adjustments and develop muscle memory. A newbie will do fine. It's the experienced players who panic and think "OMG, this is new and foreign, I need to be sticking with what's old and comfortable!". So they go through the old buy-and-sell routine and everyone posts "I'll give it 6 weeks."
Well the electric bass was invented to make the upright bass more portable and so it could be amplified. In the upright world, you have 4/4, 3/4, 1/2 and 1/4 size. All with different scale lengths. There must be a reason for that.