I would personally never buy an '07 CVO Touring bike, because of the issues with the then-new 110" engine. There are many horror stories about those. And, you don't get the new frame, etc., that was made in 2009.
The '10 Softail CVO is a completely different bike.... The 110" B engine is a balanced engine for the hard-mounted Softails, and the frame is completely different from a Touring bike. You can't really even compare the two bikes. The Softail is a very light, nimble bike (in Harley terms), while the Road King is a much larger, more comfortable bike for long-distance riding.
If you are puttering around town, or do mostly short distance trips, then the 2010 Convertible is a wonderfully fun bike to ride. But, if you are going to do long distance touring (more than 200-300 miles per day), a real touring bike such as a Road King, etc., is a far better choice. However, a 2007 touring bike is not going to get you the 2009 and later frame changes, and the many other changes, that were made on the touring bikes in 2009.
In my opinion, they are asking for too much for that 2007 CVO Road King. Frankly, I'd continue to look around...
Full Disclosure: I am a Touring guy, not a Softail guy!
Ken