We didn't particularly like our basement air in our '05 Vectra 40FD. It was noisy at night to us. Like living in a flat next to the trolly line, you adjust. Or coach had a problem with the feed stack to the roof vents separating from time to time. The last time it did my DW and I fixed it and it lasted till we sold the coach. Another consideration is the room the basement air takes up. You loose valuable storage space. If you have a side mounted radiator you loose even more.
We are not thrilled with the air on this coach but find it better all around than on the last. The roof air noise and velocity is harsh and loud. But the advantage of having zones, 2 in our case, is that we can use the bedroom zone most of the time to keep the coach comfortable during the day and the front zone at night to move a good portion of the noise away. When the day starts to warm up to around 80* we must run all the units. We have 3 units but just 2 zones. Those with three zones have more options. The basement air would not keep the coach comfortable in the TX 90*+++ heat. By the end of the day if we were at 85* inside the basement air did good. The roof air in this coach seems to have no problems cooling us off.
Storage for many of us is an issue. Because our air is on the roof and we have a rear radiator we have gained 2 compartments. But, in all fairness, this coach has full basement storage so the added rear compartments are not essential for most. Great for our needs.
As far as the rear radiator is concerned, well, that is another subject of great debate. Most don't like it because getting to the engine is restricted for many maintenance jobs, like changing the belt for instance. This is not needed often but is can be expensive when needed. I don't recall I could access anything else in the Vectra. Never had to get back there for repairs. When the automotive a/c pump went the shop went through the floor hatch.
Hope my thought help.
Rick Y