The triggers (ZL/ZR on PowerA, L/R on GCN OEM) have a little less than half the travel to reach the membrane button underneath; this keeps the same analogue/digital feeling of the GCN controller without having such a long and ultimately useless pull (Unless Smash is special and uses the analogue trigger data)
ABXY buttons feel more or less identical, and the small difference in feel I could tell when comparing side by side could just be wear on the OEM buttons. There is a tiiiiny bit more travel but I couldn't tell or notice unless I was pressing OEM vs PowerA side by side.
The shoulder buttons (L/R on PowerA, Z on OEM) are easily the biggest difference; they are much closer to the ABXY in terms of the feeling of pressing, rather than the 'really stiff microswitch' feeling of OEM Z button. Seems to pivot the same, and is much meatier of a button. As a person who uses Z for Jump, this is probably the only thing that will mess with any amount of muscle memory for me.
C Stick is ass, but C Stick has always been ass. It's a cheaper looking yellow and isn't as grippy.
Analogue stick looks ugly in comparison but is a good bit grippier; so it's not pretty but if it holds up will be better to actually use.
Sticks clicking may fuck with some muscle memory for some techniques like turnback jumps or B Reversals, but probably easy to adjust, it's just going to have a bit of extra tactility.
Shell plastic seems to be PBT vs the OEM's I would guess ABS. Rougher feeling plastic but no flex in shell; feels very solid. PBT is considered 'premium' for keyboards vs ABS so take that as you will; if I'm accurate on it being PBT it's not them cheaping out. PBT should wear less than ABS.
Honestly, the biggest differences are the triggers (good)/bumpers(preference), and the fact that the hump is much flatter. C Stick is the only thing that I can call a straight negative, and it may be possible to transplant that anyway, which I'll be trying later tonight. (Also since C Stick is mainly flicked who cares lul)
I suppose I should talk about the menu buttons!
They are all very tall, very small, and pretty close. They feel nice to press down, but it you may end up hitting the wrong button for a while.
Haven't tried Gyro, not sure I have a game that would actually play well with GCN controller that uses Gyro; Splatoon uses B to jump and BotW would just be weird. Playing Doom with C Stick? lul, I guess I can try that to test responsiveness/accuracy and DIE.
Not only does this controller wake up the system, but unlike the Joycons/ProCon, if you push a face button and it starts searching for your Switch (but not waking it up), you can press the Home button while it's searching and it'll just go ahead and wake the system up. Thank god.
Dpad is actually probably better than the Procon's. It's got a nice press to it, but it's still in a useless position and won't be good for Dpad heavy games.
Rough lag test to follow later.