I would strongly urge no one risk converting their phones right now. Parts flowing out of China are complete **** ATM. NO ONE can guarantee the same quality as a month or 2 ago. It doesn't matter what company they are. The market has completely changed in the last couple of weeks.
The main differences between the High Copy ones and the OEM (Not Apple authorized parts) are:
1) High copy backs are PLASTIC, not glass
2) Camera lens is plastic, not glass
3) Lens diffusers aren't actually diffusers and are just a silver ring with a smaller opening.
4) The coloring process of the parts is different because they are plastic, causing A LOT of color oddities (parts being more blue than white)
5) Alignment issues with retail iPhone 4 midframes and seams
There are some other obvious things such as missing speaker mesh (the moment you see this you have a fake), printing process of the letters is off, camera lens not sitting flush with the back plate.
Overall if anyone spends money on parts right now, you are taking a major gamble. It's not the same as before