I've found that the G-Max and PowerGravity toilets from Toto have been doing well.
I had the Toto Ultimate installed for over an year, and it worked nicely.
The Dartmouth does have a wider tank, than say the ADA Ultramax, MS854114SL.
Codes like to see 15" from the center of the toilet to the next fixture or wall, for a total of 30".
Since you've had a toilet there before, you will know how it feels to sit there that close, and whether your shoulders fit.
The Plymouth tank is shorter than the Dartmouth, so yes, it does give you more room.