One of the best compliments an editor can get (when you already know that the client actually likes your cuts and your workflow) is that you are fast.
This is one tendency that will brings clients back again and again. The more directors and producers start to edit their own material with editing suites coming down in price so much, the less work editors have. One way to let them leave the edits to you is to show them you are going to get their job done faster.
If you are like me, you edit with both Final Cut Pro and Avid. I did learn Final Cut Pro about a year before I started editing on Avid, but now hold Avid a tiny higher than FCP. For what? It all depends. But the one thing I like to keep the same (or close to it) is the keyboard. This makes switching between systems much easier.