@Lindenwood I want to emphasize what
@dfwatt has been saying - a simple "stiffer" vs "softer" comparison is inadequate to compare a good aftermarket suspension to the stock Model 3 suspension. At least for 2021 cars which is what I have experience with - I've read that older Model 3's like
@dfwatt's had overall stiffer suspension tuning from the factory (but maybe not
better, unclear to me).
The stock damping is just really, really bad. I don't know how to sugarcoat it. As someone with lots of twisty roads around, it took me barely a handful of turns on my test drive to get the car literally bouncing and swaying out of control. The weight was all over the place, completely out of sync with the turns and my inputs. This was obviously a 100% stock car (a demo car), so as you add grip the poor damping will presumably get worse.
Yet the ride quality stock was nothing special either. Perfectly acceptable to me, yes, but kind of bouncy and busy and you felt the road as if it were a sporty suspension...but then push it hard and it became clear it
wasn't a sporty suspension.
The M3P I bought drove exactly the same. So I don't think anything was wrong with the demo car or my car, that's just how bad the damping is on these cars for truly hard, challenging driving with lots of tight back-and-forth turns. Even in fast smooth sweeping ramps it had very delayed steering reactions and never felt totally settled...but there you could at least exploit all of the car's grip easily.
Now how much does this actually matter for autox lap times, I can't tell you. The weight not being settled has to matter some. But maybe just as big an impact would be lack of driver confidence or control.
I have the Redwood Performance Sport coilovers, which I think have similar goals as the MPP Sports. Overall yes the car can definitely ride better than stock when set of the softer end of the dampers. That bounciness of the stock damping is gone, and it rides much better over big bumps and dips. However be aware that stiffer springs will always be stiffer springs. No matter how soft you adjust the dampers to, if you go slow over bad pavement, stiffer springs just won't compress much to absorb it, where sometimes the softer stock springs could. At least I'm 99% sure that's what I've felt. That is the only ride quality downside I've experienced with stiffer springs + good dampers. The solution is simple of course: drive faster and harder and the ride literally smooths out.
Or go for a GT / Comfort kit that presumably has stock-like spring rates combined with good damping...
I think a Sport kit would be worth it for your track or autox use, and you'd be fine with it on the street. But it would be an easier decision if you also had good twisty roads around to enjoy it with on the street. Honestly you'll probably be happy either way (Sport or Comfort/GT).