There are some differences between a radiator with copper (Cu) fins compared to a rad with aluminium (Al) fins.
1. The price: copper is much more expensive.
2. The weight/density: Cu = 8,92 g/cm3; Al = 2,7 g/cm3 ; Copper is more than three times heavier than Aluminium.
3. The optics: copper red against a silverish look; also copper tends to tarnish over time, AL has a natural oxide coating of aluminium oxide [Al2O3] which is pretty much inert.
4. Thermal conductivity: Cu = 400 W/(m · K); Al = 235 W/(m · K); Copper has the ability to almost conduct twice as much heat over time than Aluminium.
Conclusion: If you are rich, like the copper looks to death, are a strength athlete or own a crane to move your rig (with mutiple Cu fin rads installed) and/or need as much thermal conductivity as possible - for instance you don't have much space in your rig and can only install one radiator - than a copper fin radiator is your thing. On the other hand: Al rads are favorable in price (~50€ cheaper per rad) the lesser weight is also a in favour for Aluminium in relation to Copper if you have multiple big rads installed. The thermal conductivity is neglectable in my opinion if you use multiple big radiators like you intend to do, because if you have fans installed and they run at low speed, the cooling capability is already overkill with those aluminium fin radiators. Nothing in a rig produces so much heat that it needs such intense cooling. You see, even pure air cooling is already enough to keep the CPU and GPU(s) in stable conditions.
