I prefer an option that allows to invert the current behavior, i.e. makes Ctrl-V paste plain and Ctrl-Shift-V paste with format (and similar for Drag&Drop with Shift Key). But I think the current behavior should stay the default option. In nearly all applications, pasting with format is the default, so as annoying as it sometimes is, it is what is expected.
See also Make optional - Turn on/off paste that converts HTML content to Markdown links.