I assume that this depends on your computer/GPU/GPU driver.

I have used Konsole for many years and I have used kitty for about 2 years in 2024/2025, then I have switched to ghostty around the beginning of 2026.

At least in my computers (with NVIDIA GPUs and Gentoo Linux), kitty was many times faster than Konsole and Ghostty even faster.

Moreover, in the now somewhat distant past when I was still using Konsole, it did not have some font rendering features that I desired, but that might have been solved meanwhile.

A reason why the terminal emulator speed is important for me is that I frequently compile big software projects and I find it unacceptable for a compilation to be slowed down by the low speed at which the compiler output is displayed on the terminal window, which happened frequently with all terminal emulators older than kitty and ghostty (I have always used CPUs with enough cores so that compilation itself is very fast, so the older terminal emulators become the bottleneck).