I have both. The Pro 2 keybed is a definite downgrade. I don't think it's a night and day difference, nor would I consider the Pro 2 keybed sub-par by any means, but you'll definitely notice a difference. It's just lighter to the touch and less substantial feeling then the REV 2 keybed.
As far as the engines are concerned, they are significantly different. As you are aware, the Pro 2 is a much deeper synth voice architecture-wise . . . and that's really saying something as the REV 2 is certainly no slouch in that department itself.
Paraphonic mode on the Pro 2 is my favorite . . . produces some really unique sounds . . . just understand it's limitations and that notes don't trigger as they do on a true poly like the REV 2.
Filters on the Pro 2 are outstanding . . . tons of variety . . . great routing options. It also adds a couple more envelopes than the REV 2 has, tuned feedback like on the Evolver series, analog distortion, and one of the best onboard sequencers you'll find on a synth. Yes, 4 delay lines available, but no digital multi-fx like the REV 2.
Oscillators on Pro 2 are purely digital, as you're probably aware. They're not particularly huge sounding, but personally, I don't think the REV 2's DCO's are either (also have a P6 . . . that thing has some killer oscillators!). There are plenty of things you can do to thicken and liven up the Pro 2's OSC's . . . far more options in that regard than REV 2 . . . it just takes some effort to make them sound good.
I purchased my REV 2 16 voice specifically for live use, and at that, it excels . . . splits/layers and true polyphony were crucial for me. The Pro 2 is a programmer's synth . . . I've had it 2 years and I'm still just scratching the surface.