I bought the LR and added boost. I think at the time the delta was 7 or 8k and the M3P was lowered a bit. I didn't want the worse ride quality and I knew with the 20" Ubers my wife would mangle the crap out of them. All the demo M3Ps I saw were curb rashed to hell. Also knew I'd need snow tires as well for at least 3 months out of the year.
I couldn't justify spending the extra money and just hassling with sell the 20" wheels and the extra range of the 18's on the LR mattered. Within a week or 2 I added boost to the LR after getting it. Worked out to be the perfect setup for me. TBH, the stock LR is pretty damn quick. I really don't use the acceleration as much as I originally thought I would.
Now after about 10k miles in of ownership, I probably would have been fine with just leaving the LR stock so to speak. My wife drives it in chill mode. The wheels are curbed to hell but actually it is the hub caps that took the abuse. I never once regret not buying the M3P. I don't miss track mode. I don't care about the spoiler and the LR is still quicker than the vast majority of cars you'll find on the street. Insurance was cheaper for me by a lot when I shopped the LR vs P but YMMV.
Now if Tesla had made a "proper" M3P, I'd be a lot more interested in it. If they had taken an approach like the 'M' BMWs or AMG Benzes, I'd like have bought in. Additionally if they ever come out with a better M3P, the resale will likely take a bigger hit since it is the top of the line so to speak.
At the current price delta though, absolutely no point considering the LR and adding boost. The P is a much better value by far. I think the LR is overpriced at its current MSRP. Doing it over again, with such a small differential in price, I might just go for the P now that the suspension seems to be the same. It pretty much is just an LR with an extra dose of acceleration boost thrown in. It still tapers off above 60 just like the LR.
So for the small delta, if you can work with the summer wheels, then go for it if 0-60 times really matter that much to you. If just using it as a fun daily driver, the base LR is still quick and fun to drive.