Phono Protractor. Recommendations?


After purchasing a new Cartridge recently, I'd like to purchase a good protractor.  There are so many available, each claiming to be the one to have, I'm confused.  
What do you recommend?
louisl
I have all 3, Mint, Dr. Feickert, and SMartractor. They are all good. I like Smartractor the best. If you plan to change cartridge more often, I recommend the Smartractor. 
Send an email to Mike Fremmer.  He knows this stuff better than anyone I know.
Is the SMARTractor more precise than the UNI-protractor? I ask because I have the UNI, and actually prefer my old Wallytractors.