usmcshepherd,
I think probably the best way to answer your question is to test drive a couple of units and make your own decisions. I think there is possibly a more complex answer than one would initially think.
People have different ideas as to what is comfortable. I know a few people who absolutely HATE A/C. Me? I like it nice and cold! LOL So what is comfortable for some on the forum might not be for you and your passengers.
There are several variables that can come into play, as well. How many people will be travelling? Do you have any pets? People and pets both add to the heat load of the A/C system.
Are the windows insulating dual-pane glass? Does the rig have a dark, full-body paint job?
Now, all that being said, you're looking at relatively small RV's so I would optimistically expect a reputable manufacturer to install the proper equipment to maintain a comfortable level inside the motorhome while travelling. However, we are talking about the RV industry, here, and "optimistic expectations" are probably not worth much.
One other thing to consider, though, is if you have a diesel engine, and a propane generator which you will be using to help maintain the comfort level, you'll probably be refilling the propane tank fairly frequently. While a more expensive alternative, if you have the option for a diesel generator, there is a lot of convenience having the generator fuel being the same as the chassis engine fuel.
I haven't done much research on these types of vehicles. I've looked at them at shows and such and browsed websites, but that's about it.
I think a couple of test drives in various units will best answer your questions to your satisfaction. Just try to arrange them on a hot, sunny day! LOL
Good luck in your search,
~Rick