The only Nitro's advantage as I see it is the slightly larger cooler. So if you're going to push your card(s) then you might want Nitro for that extra little bit of cooling capacity. Other than that Pulse has everything that a mining card needs: double-bearing fans, the baseplate that is directly cooling the vram and memory chips, and even the backplate is contacting the pcb with some thermal pads. If you're undervolting your Polaris cards then the Pulse will probably work just fine for you. If the price difference is small, though, then go with Nitro.