GPU vs GPUs Question

Not a GPU expert by any stretch. I’m using V-Ray for Sketchup 3.6… Are you better off having a higher end gpu, or two gpus of less power running SLI? I’m sure it depends on what cards, so how about this comparison:

(Qty: 1) GeForce RTX 2070 Windforce 8GB

or

(Qty: 2) GeForce GTXs 1070 Windforce 8GB running SLI

I know the dual 1070’s would be a little more expensive. I have a $550-ish budget for a card, but could probably go to $700 if needed. I was just curious if you can throw a little more money at the problem, are you better getting the best GPU you can afford, or downshifting and getting dual cards?

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