Apart from comments JP pistons were heavy and the rings rubbish the final straw was that it was cheaper to buy JP pistons from UK distributors like "red lizard" than direct from JP and even when I pointed that out to JP they refused to budge on price. JP also wanted twice the $ to ship from Aus to NZ than UK suppliers charge to ship to NZ!
Australia Post is now just about the most expensive O/S postal system in the world so do not blame JP for that, Julia Gillard yes, JP no.
As for unbranded pistons I never even think of using them.
If a product is good then the maker will want to tell the world about it, if it garbage they won't.
If a supplier sells quality pistons then they will sell them in branded boxes so the world will know that they sell good quality pistons.
If neither want their name to be associated with the pistons it is most likely because they want you to forget where you got them from before they failed & totaled your engine