Nvidia GTX 770's in SLI are going to beat the GTX 780ti in almost every way except for things such as heat production, energy usage, weight, etc. Personally I would go with SLI GTX 770's since Nvidia fixed the micro-stuttering (where one GPU renders faster than the other one over the SLI bridge and causes micro-lag). Also, what are you trying to run? A GTX 780ti is enough to run up to 3 monitors, only use for SLI is for showing off/video editing/high performance computing.