I actually bought my HTG from A51 as well, but basically with A51 you're getting more light for less electrical pull. I can vouch that A51 also runs cooler, the SGS is the coolest LED I've ran so far.
The HTG had a lot of blue so I was vegging great with it, and I know it will produce buds so don't worry about that, but it's almost old technology now. Search the boards and you will see a lot of HTG failures.
I was fine with HTG until I got an A51.. Just like I was fine with my last generation Focus, but when I upgraded to this past years model, I COULD NEVER GO BACK. lol
HTG = flank steak
A51 = filet mignon
I would recommend sending the folks at A51 an email. They are usually more than willing to answer any questions and they will have info on that exact light because they ran some tests with it before I bought it from them.