I have used Moton race and JRZ 3 way race shocks on my Porsches. Personally, I couldn't tell you the difference in performance between them. I was pleased with both. At this level what was most important was setup and support from a shop that was maintaining my car(s). I would pick a shop and go with their recommendation. Have them do the spec, installation and setup. If they go to the track often, they can even drive your car and provide track settings for you free of charge.
I would not buy them on the internet for the best price and take them to a shop that quotes the lowest price for installation. Pick a good shop, support them and let them make a little money. I believe the Engineer/Tech will make more of a difference than the actual coilover even if you are a highly skilled driver.
All of that being said, if I were to put coilovers on my M3 they would definitely be JRZ RS. If I only wanted to lower my car, V3's would be my choice. I went with Dinan springs and camber plates because I wanted to keep EDC and I did not want to lower my car.
I hope this helps.