Except for basic editing tasks they aren't really comparable. Pico (or it's clone nano) are basic text editors designed to be easy for beginners to learn and use. Emacs is a text editor that is so extensible (and so extended!) that it's often compared to an operating system.

I used Emacs continuously for two years and vi on-and-off over five years. What do I use now when I need to do a bit of text-editing on a CLI...I use pico or nano. The problem is that I don't use Emacs or vi all the time, and can't remember the key bindings well enough to use them effectively. That's not a problem with pico.

So to answer your question: as long as you're doing relatively small programs (hundreds of lines and only a few files) pico should be fine. You might want to look into nano though, it looks the same but allows syntax highlighting and is more configurable.