I've never used a replica jersey in anger, but I tried one on. The fabrics weren't as good, and the cut was looser. Nowhere near as good as a PT jersey IMHO.
The fabrics are never going to be as good when the replica is 60% of the price of PT. Both jerseys have been fitted on the exact same human. The difference in size is negligible/in your minds.
I've never used a replica jersey in anger, but I tried one on. The fabrics weren't as good, and the cut was looser. Nowhere near as good as a PT jersey IMHO.