Dear Raul, I have a few protractors mainly because I am still trying to find one that I really like. Personally, I like Mint protractor the best as far as ease of use, mirror surface and all. It is a lot easier to use for cartridges like Koetsu, Air Tight and Kiseki. However, now that I have 4 arms and most likely there will be more in the future, I don't want to keep buying new Mint protractor every time so I start looking around for universal protractor. I think Feickert is great and it has 3 geometries to choose but its finish make it harder for me to use on the 3 cartridges mentioned above. Clearaudio is fine but it has only one geometry with 4 IEC options. I figure since I spend all these moneys on cartridges and arms, why not experiment a bit more with various protractors if it may make a big enough difference in setting the arm/cartrige properly.
I am thinking of trying SMARTracker just because it seems that on the usability side, it is more well thought out that other protractors and seemed to be one that was really designed by end-user for user. It may not be more accurate than Feickert but at the very least, it would be more user friendly, I would guess.