They both sound like a good choice, I would take the Tiffin but that's a personal choice. I like Class A units.
Whichever you decide, check the manufacture date on the tires. Don't just look at the tread depth. They may both need new tires.
RV tires age out before they wear out.
Price a set of new tires for both and factor it into the offer you make on the unit you chose.
40,000 miles on an 8 year old is about 5000 miles per year. I've read that on average most RV's are driven 4-6000 miles a year. I think it's a good mileage for the Tiffin.
If you are serious about any RV, hire mobile RV Tech and a mechanic to do a prepurchase inspection.
Do not sign any agreements or give the seller any money until you are satisfied with the condition of the RV.
And don't hesitate to ask questions on the forum. Someone will have the answer.