I have heard people say the 10T's may be easier to place because the 9's may overwhelm smaller rooms with bass. Not sure whether this is due to the 4 LF drivers, which Aerial says have equivalent area greater than a single 15 inch speaker, or because of the down firing port, or both.
I can tell you the 9's are the only thing in my system that hasn't changed in the past 5 years. In my room, they have consistently presented the flavor of the electronics in front of them, and have always sounded clear and grainless, with punchy dynamics, and just a touch of warmth. Soundstaging is good due to the narrow front baffle. Bass has also been quite good but my room is moderately large with 9-foot ceilings.
I have found the 9's like the power of relatively large solid state amps. My 100wpc Lamm hybrids sounded very, very good, but did run out of steam at very loud levels. My current Clayton M300 monos are a much better match. Others that worked well include the 500wpc McCormack DNA 500 and Cary M500 monos. The 150wpc Herron M1's just didn't do it for me with these speakers. Sorry, I have not heard the 10T's.