I liked my P90D better than my P3D for two reasons:
- air suspension soooo much smoother
- Model S much less road noise; mildly less wind noise
The things that make it a toss up are price, warranty, size, ap 2.5 vs 1.0, etc.
At the right price I would take the P90D.
That being said, I had an 85D loaner that lacked air suspension (and power) - and I would take the P3D over that car 100% of the time.