Maybe it's the way I use it, but iTerm2 crashes (or hangs) fairly regularly for me on macOS. I usually need to restart it at least once a week, which means losing ~dozens of tabs with context in them.

I use urxvt on Linux, and I don't have any problems with it.

Edit: I should also mention that I see plenty of non-crashing, non-hanging bugs with iTerm2 that look like memory misuse to me: split-workspace mode (tiled with a text editor) causes wonky graphical errors, and I've seen what looked like buffer reuse artifacts when switching between monitors.