I have both.........they are great guitars, look very similar, but play & sound like very different guitars.
The 61 has a thinner wider neck with a rather fragile neck joint. If you pull on the neck it flexes very easy and feels like it wouldn't take much pressure to snap it off. It also has a much larger headstock which makes the guitar even more neck heavy and causes "neck dive" as soon a you let go of the neck......even with a leather strap. The 57 pups sound great.
The standard has a much stronger, secure neck joint. The neck is fatter and it comes with the 490 & 498 pups which I think sound good in an SG. Les Paul size headstock and slight neck dive with a leather strap. I actually prefer the Standard.
I bought both new and paid $600.00 more the 61. Buy the standard for the smaller headstock and much stronger neck joint which doesn't interfere with upper fret access. If you don't like the pups, use some of the $600.00 you saved and buy a different set.