I've been given the opportunity to check out the RTM version. I have to say this excels beyond the Aerosoft offering in many areas, and overall, I am enjoying it more. Here's a quick comparison...
The flight model feels much better. It has realistic takeoff speeds, and in general it feels better-rounded. Of course I can't make too many other comments as I've not had much time to check it out.
EDIT:After a little more testing, I'm starting to find a couple points where the Aerosoft one may be more realistic. Though my knowledge of fly-by-wire in fighter jets is most definitely less than others here.
Visually, every important part is just as good as the Aerosoft offering. In fact I find the gauges in the IRIS version to be easier to read. In the VC, I probably give the IRIS version a slight upper hand because of its ease of use and good balance between polys and textures. Though if you like rivet counting, you may enjoy the Aerosoft VC more. Externally, I give the Aerosoft the upper hand because of its considerably higher poly count. It looks like a more refined machine (as it should be considering all of the polys). However, the tail is higher resolution than the Aerosoft version. This is a big plus for the IRIS version and will certainly please repainters.
Systems-wise, IRIS's offering has the upper hand. Most of the switches are clickable and do something. I've not had the time to mess with them in any more detail though. There is certainly more to play with here than on the Aerosoft version. The HUD and displays look a little more realistic on the Aerosoft version, but I'm not too much into fighters and don't have the qualifications to comment any further on them. That being said, functionality-wise, I don't see anything wrong with the IRIS versions.
Sounds-wise, the IRIS version is every bit as good as the Aerosoft version. They both sound like F-16's I've heard in real life. I'm calling this category even.
Performance-wise IRIS wins hands down. FPS are constantly locked at 36 FPS on my quad core machine.