Bought the 4.7 inch model to replace a dropped and destroyed 5.5 inch XT. I like the smaller size, seems more "right sized" for using on my dual sport. The 6-inch would have seemed huge. So far I never look down and wish I had more screen, just not an issue. Super fast processing, as compared to the XT. While I don't use the GPS to pair/operate my phone or other comms, when I get calls on my phone a notification does pop up on the screen, so that's nice.
The XT3 also absolutely works with Basecamp (despite what Garmin says, and the popup in Basecamp). So interfaces just like every other Garmin device I've plugged into the computer. In fact it works better than my XT model did. Save tracks or waypoints to the unit and the next time it restarts it will let you designate which knew things you want to show, group them in a folder, name the folder. Pretty slick actually.
As always, being able to plug a Garmin powered base directly into an open accessory connection is perfect. The XT3 wiring is also less bulky than the XT; doesn't have the little voltage regulator box and doesn't need a fuse when wired to an accessory connection.