Not quite the same. For instance, to duplicate a line in Emacs you have to go to the beginning of the line, kill it and then yank twice, and it doesn't even work always, particularly at the end of a buffer. In vi, it's just yyp. No corner cases.

I've been using emacs for a long time. When I duplicate a line I don't even know that I'm following the steps you mention, I just do it on autopilot.

What I like most about emacs though is that I rarely have to do repetitive tasks because I can write a bit of lisp code to do them instead.

Or you can go to the beginning of the line, press Control-space (set mark), press Control-e (end of line), then Meta-W (copy), and Control-y (paste).

Just to share experience, i've recorded Macro named dup-line and bind to `C-M-y`. And find it very handy :)