Of all tested terminals xterm is faster only than konsole.
Startup is instant too.
It has comparatively very good "fidelity", giving usable screen outputs with most applications without tinkering.
A factor of 2x in throughput is nothing to sweat about I think, given that xterm is fast enough.
Haven't verified the benchmarks in your link, and not tried kitty, but I believe the bench did not test xterm with bitmap fonts which I believe are significantly faster.
I'd also look at CPU rasterization performance. I often don't have graphics acceleration available (in a VM).