I did report back some time ago on the difference in Roadtrek vs Interstate.
I like the E-trek system of the RT: more batteries, no generator underneath. Inverter system powers ALL the 115 v electric: TV, m-wave, larger 7 cu ft fridge, A/C, outlets. Much larger solar panel on RT. We use a 115 v magnetic induction cooktop.
Slightly smaller A/C but I feel that RT does a better job of insulation in the sidewalls and roof.
RT has smaller water & waste tanks by a few of gallons.
I really was disappointed with the half bath room door in the AI and the RT does have a better bath door system but the footprint and quality of the AI bath inside is better and better quality. RT has eliminated the exhaust fan in the bath now.
No Suburban propane in our RT, instead a diesel powered heater and hot water system or you can get a propane hot water system.
Cabinets: prefer the AI except that RT uses latches on ALL cabinets, although they have many issues with the latches since the wood in the cabinets shifts, swells, etc and you will probably have to learn how to adjust the latches: I have.
Overall fit and finish on cabinetry I like the design of the AI. Mechanicals I prefer the RT.
If I had the money, I'd buy the Advanced RV!