I am a huge fan of primo simply for nastalgia reasons. It was my very first cycle, I used to include it in all my early cycles before I ever used deca and I always had great results with lean mass gains. This was long before it became so rediculously expensive.
Both products are great, although I prefer Masteron,,,I've used it much more, and like the results I've gotten. As for hair loss, I wouldn't know, I have a shaved head??!!!
primo is great if you want to use it long term and keep all your min. gains..100mgs EOD is great and no hair loss i know of.
masteron is a great drug if you want short term gains with a great polished look.. hair loss is a very big threat with masteron and i would only use it for a show the last 6-8weeks at 100mgs EOD..
I love the look i get from masteron weather it is summer or stages