[Chance]

For the climates where you need AC in a van I don't think the variable speed compressors are much of a benefit when it comes to power consumption. If you only need 2-3k BTU to maintain the temperature the battery capacity problem gets really easy to solve. It does help a lot with noise and humidity though. I'm not sure if RV roof AC's are even using TXV's yet...

An exception would be if you camp mostly during days at campgrounds with shore power, and can therefore power A/C with 30A service so installing a larger unit makes sense; but at same time occasionally boondock at night and need to power A/C from batteries (with or without inverter).

Some units that can operate down as low as around 30% of rated capacity by use of variable speed also gain efficiency by running much slower, similar to mini-splits. I’m interested in 8,000 BTU/hr dual inverter window air conditioners because they are inexpensive, and EER are +/- 15. It also means SEER rating for nighttime use should be even higher.

 

[Chance]

Everyone's use is different but I would opt for the larger Rec Pro because it works, is quiet and relatively affordable. The smaller Rec Pro is a second place but is less capacity in a compact casing and therefore noisier and less efficient.

Since a lower-capacity air conditioner does not need to move as much air flow, and heat exchangers don’t need to be as large, doesn’t it follow that a 9,500 BTU/hr unit can be much smaller than a 13,500 unit while still having similar sound and efficiency performance? I’m not that familiar with RecPro efficiency data yet, but expect smaller size doesn’t necessarily mean extra noise or less efficiency when cooling capacities are much different.

I helped install two 9,500 recently and know they are fairly quiet compared to most common RV units. If 13,500 is even quieter, that would be great, though probably difference would not be that noticeable. The 9,500 is so quiet that there’s not as much room for improvement.