IDK what that person is looking at or really comparing there because they are indeed different. I’ve worn each to compete and P99 is quite different than GS and the predominant larger top pick and bottom picks is some of the main features of why I love it.
:think: So did the P99 also feel different on footwork or even more basic, just simple edges and stroking?
I remember being quite surprised at the GS's rather smallish toe-picks, because even my old blade had bigger (and sharper!) ones (also cross-cut), even though it was just a lower level blade. Although I didn't feel any difference at all on toe jumps or toe steps, so it didn't matter in the end.
.......................
To the OP: I can't comment on P99 vs. GS, but I switched from an Ultima blade to GSs.
In direct comparison the GSs have felt much more 'alive' on the ice, more agile but also less stable.
It's true that they're no gonna help you with mastering footwork that you don't already know how to do i.e. you will still need to know the mechanics of how to f.i. make a 3 turn or rocker happen, or how to position your shoulders and upper body to execute a choctaw. But I definitely had to work more on my old blades to get them to do my bidding, whereas on the GSs footwork feels smoother and not as rough.
They're also definitely less scratchy because the spin rocker to drag pick geometry of the GSs is so much different compared to Ultima models.
Although my crossovers were never noticeably scratchy, I always had to pay some attention so it wouldn't happen on a few strokes here and there. With the GS I don't have to do that anymore.
Also my Sal and Loop take-offs used to be pretty scratchy, there were always drag pick lines on the ice. That has instantly changed with the GS, and now it's just a clean curve with one nice, little hole from the drag pick where I have left the ice, even though I did not work on or change my technique (although one could make the argument, that maybe I had to readjust my position on the blades because of the GS's different spin rocker, and that has led to me unconsciously shifting my weight further back

).
ETA: I just remembered, a friend of mine (skated competitively as a kid) went from one of the higher level Ultima blades to an MK Pro I believe, and observed the same thing on his jumps.
Also my back inside loops 9/10 (at least!) used to have scratchings from the drag pick on the ice (although admittedly I had stopped practicing and trying to improve them a long time ago, because uh, I've got no discipline and outside loops are easier and a 100 times more fun

).
But with the GS they instantly went to only 1/10 having those marks and are mostly clean (
if I do them at all

).
I can't do any spins, but on my um, let's call them failed spin attempts, the GSs turn very fast, especially on sit spins. Compared to my old blades it's like riding a wild horse.
Now all this might sound amazing, but keep in mind that I'm comparing GSs to an Ultima blade. It is very possible that you would get the same or similar results with a much cheaper, intermediate level blade from JW or MK, i.e. Coro Ace or MK Pro. I haven't tried these, so I can't say for sure (the only reason why I went with GS was their 8 feet rocker... oh and people saying how nice they are for footwork)
I'm also not sure I'm a fan of the added grip of the side-honed edges of the GS (at least I think that's what it is).
Another thing to consider: The spin rocker is very curvy and when I first switched to GS blades, I was constantly rocking forward onto my toe-picks. It took about 2-3 weeks until I had fully adjusted and it didn't happen anymore.
A fellow skater from my group had the same experience, and I don't know for how long she tried, but she switched to another blade pretty quickly.
I've also heard of one of the more advanced kids at my rink, that tried out GS blades and gave up after an hour because she couldn't handle the rocking sensation and I guess she wasn't prepared to invest more time to see if she could make them work after a longer adjustment period. So it's not just adults and/or lower level skaters who may struggle with this.