If the primo is real, that's your best bet. Otherwise eq is awesome, and I don't care for deca. I might use it if it were free, but I would have to think about it.
IMO i would go for the eq. why? cause its very hard to find real primo. often even your source doesnt know its fake ive seen alotta posts like that. plus any primo you get nowadays is not cost effective because primo is definately one of the more expensive ones and to get that big on your face when you look at the mirror, you need a decent amount, and its gonna cost you.
eq is almost as good as primo, its right up there, and it costs less and you dont have to worry about fake juice. if your 100% sure its real, and $$$ isnt a concern, than primo. but thats rare, so id go with the eq. deca isnt even worth considering, the bloat will piss you off, eq is almost as good with maintaing size and it'll still keep you lean. deca is overrated.