I’ve had both and can’t recall there being a difference TBH - the “T” went on when the first 1290 Super Adventures came out to distinguish the difference.
They all go well, stop well and handle well. You can get proper laugh out loud ludicrous performance, along with long distance comfy cruising plus reasonable off road capability if you want it. (Edit - having had various GS and GSAs over the years, they just don’t come close in my experience)
There’s loads of extras you can add to make it comfy (get rid of the standard seat straight away). Doubling up the screen mounts turns the standard screen from a liability to something actually quite comfy. Bumot or Mosko Moto soft luggage fits well, and the GPS mounts are solid and secure.
These are easily in my top two best bikes I’ve ever had.