I agree that the P3D suspension is too soft.
There's a freeway transition ramp (405N carpool to 55N) with a raised expansion joint in the middle of a curve. When I drive over it, the rear end compresses, hits the bump stops and bounces up, momentarily unsettling the rear end. It's far from dangerous, but it's definitely not a confidence-inspiring reaction. This happens, of course, on other roads in similar conditions. The demo P3D I drove felt identical.
My BMW 435i has adaptive dampers, and overall that suspension system is more buttoned-down than the one in the P3D. There is no bounciness or bucking. I drive both cars on the same roads and the difference is not insignificant. That same freeway transition ramp produces no drama in the BMW. That being said, there's more body roll in the BMW, and I can never seem to find the perfect setting (Comfort is Buick-soft, and Sport is just a tad too harsh on sharp bumps).
I think Tesla listened to the feedback about the early Model 3 suspensions being too stiff, then went too far into the opposite direction. Really would have preferred the Performance model to retain a stiffer setup.
Thats interesting that you think the 435 with adaptive suspension was better, because I just turned in a 2016 435 (estoril blue) with almost every option, including the track package which had the adaptive suspension, and I feel my model 3 performance is markedly better from a handling / suspension point of view. I am not a track junkie, having only been to a track to drive a coupe of times. I do like to have a bit of fun on onramps etc like most people who buy cars in this (or that bmw) class.
I know a lot of this is subjective, but its very interesting to me the very different opinions coming from the same base.