The standard task manager is extremely basic - the only reason I use it is to select a process to kill. The resource monitor on the other hand is clunky in behaviour (why are the handles not updated when I select an entry? why the extra step of a checkbox?), often confused (I've had multiple systems with CPU usage not adding up to the total, services missing from the list, etc.), and missing some behaviours (why can't I copy text/data from it?)

The Process Explorer from sysinternals is way better, but I also don't find it intuitive. Most sysintrnals tools seem to be a kitchen sink of awesome tools with no UX. Especially the Process Monitor filter setting dialog is annoying every single time.