When comparing spectrwm vs twm, the Slant community recommends spectrwm for most people. In the question“What are the best window managers for Linux?” spectrwm is ranked 11th while twm is ranked 39th. The most important reason people chose spectrwm is:
Spectrwm behaves largely like Xmonad (which is a good thing) without the ~700 MB GHC dependency and with plain text config files
Question Ranking
Pros
Pro like Xmonad light
Spectrwm behaves largely like Xmonad (which is a good thing) without the ~700 MB GHC dependency and with plain text config files
Pro Has a plain-text config file that it can reload while it's running
The config file can be reloaded while the WM is running, allowing the user to see the results of editing the config without logging out and back in again.
Pro Sane defaults
Inspired by xmonad and dwm, spectrwm has defaults that any normal user would enjoy rather than using an odd language or asymmetric window layouts.
Pro Straight-forward
Contains a basic set of options and doesn't require a language to configure it.
Pro Great for beginners
The defaults, simple design, and plain text config file make spectrwm a fantastic WM for those who aren't that familiar with Haskell, for example, and who just wish to get something substantial up and running.
Pro Supports floating windows
Spectrwm offers built-in keyboard shortcut support for floating windows.
Pro Was adopted as the default window manager for X11
twm was renamed Tab Window Manager (from Tom's Widow Manager) when it was adopted as X11's default window manager back in 1982. It was left behind many years ago but still stands as the foundation for every window manager that followed.
Pro Provided the base code for many other window managers
The code of twm was often built upon to create newer window managers such as FVWM.
Pro Simple and fast
Cons
Con Difficult to master
It does take time to learn the ins and outs of all that can be changed by editing the configs. It can also take some time to finally attain a configuration that is perfect.
Con Can be difficult to use
Most aspects of twm's interface operate differently than the more common UIs used in computing, thus reading the manual will more often than not be a prerequisite to using it.