Your current card has Blower (Reference Cooler) however Galaxy version has Twin Fans (Non - Reference Aftermarket Cooling).
When doing SLI, Blower is the best option since it dissipates heat faster than fans. Its vice versa for single GPU configurations.
One more thing, it does not depend on the company, it depends on the core used which would obviously be GK110 and clock / shader / memory speeds. The closer they are the merrier it is for you since one of the cards would get underclocked in order to match with the weaker card.
I would highly suggest you to buy your other card from EVGA as well. The company is very good and the reference cooler is very good. Especially beneficial in SLI.
If you buy from Galaxy the factory overclocked card (1.01 GHz) would run at 941 MHz (EVGA).