Help, please, should one upgrade to IE 11?

no

IE 11 is certainly better than any previous version of IE. And it hurts nothing to have multiple browsers on a machine, unless you're way short on disk space (in which case you probably won't be able to download IE 11 anyway).

There's no real harm in it. Even if you don't use it, there are a handful of programs that use IE as a backbone, but that's become less and less frequent these days. It would at least provide a bit better security in those situations.

if you want to upgrade yes