dont emulators inherently lag? and that's why retroarch has a run-ahead feature to fight it
I'm not sure about that but wouldn't be surprised if it's like a few MS or something. I don't think it's anything perceivable by humans.
I do know that my retropie setup has no perceivable lag, so that compared to Gamer Pro was night/day difference.
MAME cab also doesn't have any input lag but that is also using a CRT.
Both retropie and MAME cab are using retroarch under the hood.
Ever since I got really into SF4 back when it came out is when I got super sensitive to input lag. Before I got into it competitively I was not bothered by input lag and didn't notice it myself. The only reason I started was because I got serious about SF4 and started going to local gatherings, and they were playing on lagless monitors, and my moves wouldn't come out. And the reason is because I was doing them late, because I was used to that playing at home.
I then went out and bought a lagless monitor myself and started playing SF4 on a 21" monitor instead of a 50" DLP. And since then, I simply cannot play anything with input lag. It just completely ruins it for me.
But, I also get why some people may not be bothered by it or perceive it, because I wasn't even aware it was a thing for a long ass time. I wish I didn't notice it. But it's not really possible to be competitive at games like fighters if you're playing with any input lag due to the nature of having to react.