I love talking about nuts! Seriously, when my friend and I start talking about "nut width" on our guitars and mandolins, his wife cracks up every time!!
I'm a big guy, with big fingers, and much prefer wide nuts.
I would THINK (assumption here) that you would be MORE likely to get a regular width and wish you would have gotten a wider one, than get a wider one and wish it were smaller.
You cannot change from a small to a large if you feel like it - fretboard has to be built that way. I switched from small to wider and will never go back.
Only way to know for sure is to play both and see which one you like best, if at all possible.