Most people wont be using it, but if you have the option to use it, the timing is way tighter than midi. Not installed on the XL by default, only the studio versions.
I am now using it to sync up 2 mpcs. I didnt have the chip on my 1st XL, so I found one off ebay (pretty uncommon). Bad thing about syncing with midi is that then you are also sending over all the other midi data along with the timecode, and that was no good for me.