It's not clear from the link you posted whether that unit has an electric heat strip. It also states that the Atwood has a CFM rating of both 330 and 360?
The Coleman Mach 8 (15,000 BTU unit) has a CFM rating of 300, is 4 inches shorter than the Atwood, has two motors like the Atwood, and has two rather than Atwood's three fan speed settings. It's interesting that this Atwood unit has higher 'effective' BTU ratings than the listed ratings. Sounds great if true.
In our experience with Arizona-like heat in a 2552 with the Coleman 15,000 BTU unit and dual panes windows with shades drawn....we could cool the RV down by max 20 degrees.
- Mike