That's a topic that has been widely discussed. Do a search to find all the posts on the topic. Each has its pros and cons. Cruise Air is typically quieter and works very well to cool the house when parked. It is a more expensive AC with the condenser mounted in the basement and the evaporator remotely located upstairs. It's shortcoming is when used for cooling when over the road there are times when the heat radiating from the highway does not provide sufficient cooling air for the condenser and the unit shuts down. A lot of buses with Cruise Air also have OTR so it is rarely used for cooling when traveling.
Roof airs may be noisier due to their location. The big advantage to roof airs is they will work well when the coach is in motion because the condensing unit is not picking up heated air radiating off a highway. The units are much less expensive than Cruise Air units and replacing them is easily done because they are readily available at almost any RV dealer. By having roof airs some bay space is freed up for other purposes. It is very rare to find a coach with roof airs equipped with OTR so they are the only source of AC whether in motion or not.
Both types have about the same cooling expressed as 13,000 to 15,000 BTU. Both types will draw about 13 amps when running and the converter decides whether they are run solely via shore or generator power or if they can run through invererters while driving.
The debates which have taken place in the past regarding OTR, Cruise Airs, and roof airs is all but over. As coaches are being outfitted with more than 2 slides OTR is impossible to provide because of the lack of a means for ducting. As more slides are being offered, bay space is being reduced as a result of the need for structural members and this makes the use of basement space for cruise air condenesers less available. Weight distribution also becomes an issue so I predict the days of Cruise Airs in coaches is drawing to an end.