There is not a huge difference between the LR and P front brakes. Basically a slightly larger rotor size. See the wiki below for in depth info.
Before I get into my personal perspective, I'll preface with my Tesla experience. I've bought a Model Y LR, Model 3 LR and Model S LR. They have all been purchased within the last 9 months. Notice a pattern?
On every one of these I debated between going with the P version or not. I could have easily bought the P version of each model. For me it wasn't about the price. It was basically because I didn't think they were the extra money. Other than a bit more power (or lot more with the S Plaid), most of the stuff was just bolt-on baubles I could add myself. The one area where that isn't the case is track mode which I wouldn't use much anyway.
The decision was even easier for the 3/Y as I couild add acceleration boost. That was the only thing I wanted out of the performance "upgrades" you got with the P model. Excuse my sarcasm when I say "OOOOooo red colored brake calipers. Oh yeah, a stuck on rear wing. OMG - look at those metal brake pedals. Hell yeah, I want me some of those heavy ass big, non-forged wheels." Maybe if I was in a 10th grade shop class that might have been my idea of performance upgrades.
So when I looked at it all, the best course for the 3/Y was just to get acceleration boost. I have pretty good ride quality and only give up a little off the line to about 25 mph acceleration capability. For me, a total non-issue. I don't feel I missed out at all on the P versions. The only LR version seriously lacking vs the P version in acceleration is S LR and running high 10 second quarter miles is a hell of a fast street car anyway.
I can assure you if you mas the throttle on the M3 LR and you are disappointed, you will feel the same way with the M3P. The car is seriously quick. Very few things are going to keep up with the M3 LR on the street other than another Tesla unless you spend 2-3 times the price. Every time I hit a pothole I am reminded how happy I am that I don't have those horrendous wheels and how badly they impact the range. Every time my wife drives the car, I don't am thankful we don't have them easy because they would be curbed to hell just like all the demo performance cars I saw.
I have no FOMO at all. If I did, I would what until the next version came out. And the next. And the next. The performance models are the ones to be more likely see the greatest depreciation as they matter most when they are the best. When the new P model comes out, yours is yesterday's news. While it may still be a fine car, if you bought it because you wanted the "best", then you no longer have it.
When I ordered my S LR, I think the Plaid was 40-50k more. I made a decision to pass on it, and buy the Y LR and the S LR instead. At the time the diferreence between the Y LR and P was 8k. Easy choice to save the 8k and give back 2k to buy boost. When I ordered the 3 LR, same delta of 8k. Again easy choice to buy the LR and add boost. Elon has said they will be rolling out track mode to the cars with Boost. Who knows how long since it is on Elon time but it should be coming. I'll take the money I saved and invest in Tesla stock or sometihing else. Maybe in a few years the savings will buy me another Tesla. I think currently the only model it makes sens to buy the P version of is the Y. The delta is just too close.
As others have said, you get used to the acceleration pretty quickly. I thought my 3 LR stock was a lot slower than my Y with boost. On paper they are pretty close. When I ran Dragy on it to hard numbers it was actually quicker. I am already used to the Insane mode in my S LR which does 0-60 in about 3.1 seconds (factoring in rollout). So if you compare it to the M3P in similar terms the 3P is 3.1 seconds and the S LR is ~2.8 seconds. At some point, the P, LR, or even Plaid will start to feel slow.
So if you want the P, get the P. If not the LR with boost is almost as quick and better on bad roads. Keep in mind that if you use all the off the line acceleration Teslas have you are going to eat through tires. The high, instant torque, is a recipe for tire destruction. A friend of mine chewed through the tires on his P in 8k miles. He is spending more per miles on tires than energy.
Heck, the base 3 LR is a quick car. I had a friend who bought it and still hasn't added boost. He said he is saving that option for a year or 2 later when he wants to feel like he has a "new car" again. I can understand that approach.
Enjoy whatever 3 you buy. I think they are all good choices.
