If you're talking about cartridge bearings, I don't think a split crown race would make much difference. The inner and outer rings of the cartridge bearings will bridge the gap, and if the ball crosses the gap and that ball doesn't carry as much load (of an extremely minute amount of difference) while doing so then the adjacent balls will simply carry the extra load.

If you're worried about the gap, you could position it to the left or ride sides, as the front would probably have the most load followed by the rear. Folding bike top cap/nut are supposed to be tightened to 10Nm, which is really tight, so the there is quite a lot of compression on the rings, so for folding bikes I assume there is absolutely no difference in performance wither you use a split or continuous crown.