Well, I'm definitely no expert. But I agree that the first one is a sound type of bus -- Blue Bird with Cummins.
New tires? Brand new? Or just new to him, better than the previous ones?
A/C? Definitely worth something. Again, verify that they work well.
The second ad has expired, so I cannot say anything about that one.
Overheating in the mountains is more a question of the condition of the specific bus' cooling system than the brand or other general criteria. (That said, some people worry about engine cooling on rear engine buses -- because there is no head-on air flow into the radiator.) My Millicent is a longer version of that BlueBird on Craigslist, and Millicent seems immune to overheating so far.