Online is the way to go IMO, but it can be a bit overwhelming at first.
What I did was practice for a few days before hand to ensure I knew where all the buttons were, was familar with the way everything went...etc.
That said, it went really easy. I know some still hold on to the phone thing, but for us it was an advantage to use the online system, we got Le Cellier. If I would've waited to call no chance that would've been there.
If you are staying onsite and have your ressie number handy you can enter it into the computer (find the window) and it will open your +10 days.
So best thing is familarize yourself with the online booking system and it is a breeze....good luck!