Ok Pierods, now I'm confused too.
The N90s would be no slower, it simply requires auto focus lenses that have an aperture ring if you want to shoot with manual exposure settings.
With the N90s and non"G" auto focus lenses you could:
2 focus with a half push of the shutter button using the right index finger
3 set aperture with your left hand that is already there supporting the lens
4 set time with your right thumb using the wheel
There is no extra step, nothing to slow you down.
The real advantage of cameras with two finger wheels is that you can use "G" lenses if you want.