I used twm for years, from maybe 1995 to 2015 or so. It's very lightweight, not using much memory, and extremely fast. I switched to using i3wm. My patterns of use of xterm in both are different. Using twm, I treated xterms as disposable, quitting out of them often, moving and resizing. I also used vim's internal windowing a lot more. Using i3wm, I keep the same xterms opened in the same pattern, so that I can use alt-h/j/k/l to move between xterms with nearly the same keystrokes as I use to move around in vim.