There's simply no comparison. I wrote a program that prints mpeg videos to the terminal, and used it to stress test just about every terminal out there. Nothing goes faster and smoother than KiTTY. Alacritty is no exception; in my experience it had glitchy rendering for certain characters and lagged. The only terminals I've seen that come close to KiTTY in terms of textmode graphics performance and overall quality, are probably PuTTY, Gnome Terminal, and Terminal.app. The only bad thing I could say about KiTTY is it glitches for me on occasion when rendering Emacs windows side-by-side. See also https://justine.storage.googleapis.com/printvideo.html