I like the looks of a down locker on small rods or very light rods. But it doesn't really make any functional difference. The balance may change a little bit....but that amount of change will be determined by the distance the reel has been moved and by the weight of the reel itself.

Like Steve (MWCFR) said, pick what you like. That will far outweigh any of those other miniscule factors. And Steve is right about there being a lot more choices for uplockers than downlockers. Downlockers used to be the norm, but they have kind of fallen to the wayside and uplockers are now much more prevalent.