Personally, for pitch bend and adding LFO vibrato, I'm fine with either wheels, or more of a joy stick. The drawback, though, is if you want to use a mod wheel (that doesn't have a spring return) to set Expression (#11) and leave it at a certain position. If the control is spring loaded and snaps back, you can't set it to a specific expression. On the A88Mk2, though, you could use one of the rotary controls to do that. Or, use a foot pedal controller (personally, I've played a lot of Hammond B-3, so controlling volume for me with a foot pedal is pretty natural for me). But then, you'd have to decide if you just wanted to control Expression #11, or Expression #11 and Volume/Dynamics #7. For me, it depends on the VI. With some, I only want to control expression. With others, I might like to control both. One quite unique thing about that A88Mk2 is that it has a sustain pedal input, but then, it has not one but two additional controller inputs. So, you could conceivably use two variable foot pedals. One for MIDI #11, and one for MIDI #7. Adding wind control with a TECControl would also be another option. Lots of ways to get things done. I guess that's why there really is not MIDI keyboard controller that everybody is using. We've all got various tastes and preferences.
I will say, when it was working, the touch strip on the S88MkII was handy for specifying vibrato amount.
OTOH, I've discovered that a joystick that isn't spring loaded (like the additional one on the Kronos) is really idea for vibrato control with instruments that can control speed and depth. You can set speed on one axis, and depth on the other, and really get a handle on things with a single control.