The 1300W has peak efficiency at 50% load, but it stays above 90% up to around the 800W range which would be okay for around 1.35TH on one of these based on what I've seen from other results.
The 1000W unit does about 89% efficiency at the same loading, so they're about the same.
I don't really want to buy another PSU though haha, though so I guess I'll have to live with the 88% efficiency at full load on the 1300W; which is still quite good from what I understand.
I have 4 evga 1300 g2's
I run 8 sp20's
I use the settings above each evga does about 1200-1215 watts for 2 sp20's
I get about 2150-2220 gh running the 2 sp20's