The difference should be pretty subtle. With regard to fingerboards, I find the difference between ebony and rosewood to be primarily one of feel and durability -- ebony being a little smoother and more durable. Still, in my book, nothing beats Brazilian rosewood for a fingerboard. With regard to bridges, it seems that there may be more of a tonal effect due to the weight, dampening, and density differences. Yet, given the small size of a ukulele bridge and the limited tension of the strings, I suspect that it's less pronounced than on guitars (which, admittedly, is from where most of my experience is derived). However, classical guitar builders seem to favor rosewood for bridges because there is less dampening than with ebony and because they are lighter in weight. I suspect that rosewood might have a slight edge here too.
Pick the look that you like -- the difference will likely be small.