Our rig has basement air and we are happy with the way it performs, although we have not been in extremely hot weather. I like the fact that we do not have AC units on the roof, both from a weight standpoint and streamilining. We also don't have AC fan noise to compete with conversations in the main living area, a lot of times we can't even tell if the AC is on.
One drawback is the AC unit is directly under the bedroom, some people have problems sleeping when the AC is on, we don't.
Poor performance from basement air is sometimes caused by leaky air ducting.
Denny, Connie & Shadow (former barn cat made good)
2000 Itasca Horizon, Cat 3126B, Freightliner Chassis