You have pictures to back that up? Not just photos if a canopy either. I ask cause I know what HLGs can do. Only time I used SFs in flower was in tandem with a 315 CMH.
The most noteworthy differences between the two should be that hlg uses lm301hs and sf boards use lm301bs, and that the sf boards have a mix of warm and cool whites while I believe the hlg boards have all whites of a specified temperature (I've seen the single boards in 3000k, 3500k, and 4000k, and the listings for their rspec and bspec etc boards list the temperature of the whites).
Doing some digging people estimate the difference is 2.7-3.03 μmol/J for the lm301h and 2.7-2.8 for the lm301b. The temperature thing is neither good nor bad; HLG allows you to customize more but if your grow is small in scale and this is going to be your light for the entire grow you would likely choose to get a mix anyways, though you could just get 3500k. Having warm and cool whites accomplishes a similar thing.
Aside from that it's just about the actual count of the LEDs and the driver that will determine the brightness since the shape of the boards isn't all that different.
I will say I don't own either and I'm not currently in the market for a board but I'm happy with the ones I got (shown in my earlier comment). I like the ridged aluminum heatsink the hlg kit comes with but I wouldn't be crazy about doing the assembly personally even if I understand in theory how to do it.