Need general info on common lisp, opinions sought

[gnuist]

Is it good to have the following line in .emacs file?
(require 'cl)
Is it going to cause any tradeoff or only pure additions?

How is common lisp different from emacs lisp?
Where is the documentation on linux system?
Is it more than it or less than emacs lisp?
Which should I use and why? I need info on people's taste on this subject.

Opinions sought!