Outside of different pieces of wood react different, here's my thoughts:
-Design. The 1st one has retained more reflex and will have higher early draw weight as Don suggest.
-10 lbs difference in draw weight. I know you are using 10 gpp as the standard, but it's less stress on a particular design to have less draw weight. For instance, if you would have tried to get 50 lbs out of the 1st bow it likely would have taken more set and wouldn't be near as fast.
-Your second bow is actually producing almost 10% more energy than the 1st
-If on your 1st bow you left the outers stiff (non working) and the second one you let the outers bend, then how is the working length the same. If you can pull off a small working area and minimize set doing so, it's a recipe for a fast bow, assuming you don't have excess mass. Take a look at some of the flight bows.
Hopefully Steve can chime in on his mass estimation. I'm just starting to weigh my bows and there's a lot of assumptions you have to make when coming up with a goal weight for these r/d bows.
It may just be my eyes and the photo, but the area of transition from deflex to reflex on the 2nd bow looks thinner than the surrounding areas in the braced and un-braced photos. It looks ok at full draw so it may just be the pic, but that's an area that is easy to scrape too much on. Any set there as Steve mentioned on your 1st bow will rob your speed.
And lastly, 160's with 530 grain arrow at 53 lbs isn't bad at all!