Masteron, NPP, and Deca are all different forms of anabolic-androgenic steriods. Cypionate, Propionate, Enanthate, etc., are the esters that tell you how often you need to inject each steroid. So for instance, if you have Masteron, NPP, or Deca enanthate, the enanthate is what you use to know how often you need to inject them, which would be something in the area of 1-2x per week (depending on how many MG you want to take). Whereas, if you had Masteron, NPP, or Deca Propionate you would use the propionate to tell you that you need to inject them every 2-3 days.
Enanthate and Cypionate are similar and all longer-chain esters that have a longer half life than other esters like Propionate which is a short-chain ester needing to be injected more frequently than En. and Cyp.
Basically, each steroid will come in the form of X-Proprionate, X-Cypionate, X-Enanthate, etc. Which ever one you choose (for example Masteron Proprionate) will tell you how often you have to inject them due to the half-life each offers.
To answer your question about Masteron En. vs. Masteron P: if you choose Masteron En you will probably inject it 2x per week due to the half life. Whereas, if you choose Masteron Prop. You will need to inject it every 2-3 days. The difference is, one works faster than the other. As far as results go, I doubt one is "better" than the other. Although, if you need to inject anything every 2 days, I would imagine it's going to cost you a lot more to run a cycle vs. something you only need to inject 2x per week. Hope this helps