@Thomas-Neumeyer It sounds like your situation is much like mine. I started using MRA after buying the Garmin, and like you, I appreciate the fit of the XT in the motorcycle instrument space. I did carry a tablet one one extended trip for the sole purpose of creating or modifying routes using MRA, but I found it slow and cumbersome. On later trips I carried a laptop. The tablet now lives in the kitchen as a recipe server, I've owned three or four and never found them particularly convenient.
One Garmin feature that I appreciate is weather radar, using the Drive app. The traffic notifications are useful as well. The phone stays tucked in the tankbag. Can you comment on those features in the XT3? I'm assuming the Tread app has similar features to Drive.
I'm curious, how do you transfer the GPX files, hardwired connection or phone app?