Before we introduce other brands and products into the discussion, it would be hard to compare a Rev10 pod to the pods from other brands.
The Rev10 is a 10-inch speaker as compared to the XM9 which is a 8-inch speaker. However, the XM9 has a short depth but wide pod proportionally. So there is not that much pod diameter difference as would be expected with the speaker size difference. The Rev10 is substantially deeper but adds little pod diameter beyond what is required to facilitate a 10" driver.
The Rev8 fits the XM9 8-inch class based on cone area (within 5/16" of one another), and has an equivalent pod displacement. however, the Rev8 is proportionally much deeper with a much smaller pod width.
The 10" Rev10 is definitely the way to go IMO, as it gives you two/thirds more surface area than an 8" and 75% the surface area of twice as many 8". Not to mention that the 10" and larger pod deliver deeper midbass extension.
If you are going to run a pair of Wetsounds Rev10s at the radius, corner of the tower, or a more vertical (but leaning) portion of the tower, you will want to get the Wetsounds swivel collars.

David