I agree generally with the previous responses, but I'd like to add another factor that may affect your decision.
For vertical shooting with the MB-D100, the focus area selection pad is a bit far from the vertical shutter release. I have average-sized hands, and it's not quite possible for me to keep my first finger on the release and my thumb on the pad at the same time. If I place my second finger on the release, I can keep thumb on the pad, but this hardly feels natural. By comparison, the F5's setup is "just right" for me - I can depress the vertical release as often as necessary while simultaneously switching the main focus area with my thumb.
Having said the above, I'm glad I purchased the MB-D100, mostly for the added leverage when shooting vertically with heavier lenses.