I can only speak to JD as thats what I bought from my Cuda. I will say that I am very happy with mine, but I do know that as the time I bought mine you really had to select the one you wanted from a population at a show. Iv'e read many posts here and other forums about bad experiences and good experiences with almost all of the manufacturers (except the one you mentioned). I do know that the pads that were done using plastic frames looks bad and I am told warp.
I am not sure what Roseville is selling, but I suspect it is decent.
No you don't have to install it right away, I had mine in storage for probably 2 years before I put mine in. Of course you need to protect it.
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)