I took my time and asked some months ago what Spitfire people could recommend for FS9 (there are four commercial packages now). I then thought about the one by RealAir, knowing the quality of their SF260 for FS2000/2002. Then I decided for upgrading the SF260 instead, and forgot the Spit.
Yesterday I became proud owner of the RealAir Spitfire XIV, with a Griffon engine instead of the Merlin. and again I find RealAir to be of top class when it comes to quality of super-crispy VC, flight model, and visual presentation. (it even does not offer a 2D cockpit, for the VC beats most 2D-pits out there anyway).
If you love to fly these old things in FS, I strongly recommend this baby. It is miles away from the FM for the Spit in IL2 - this is the main message I have for you. I do not need to write a long essay myself, since avsim.com and RealAir both have very good and detailed reviews available with which I 100%ly agree.
http://www.avsim.com/pages/1204/raspitfire/raspitfire-new.htm
http://www.realairsimulations.com/content2.php?page=henriques1
It is the only aircraft I know of where you can really cripple your engine and so you need to keep an eye on oil temperature. The flight model again does wonders and is said to be very close to the real XIX/Griffon. sitting in this thing, you are riding sheer brutal power, and the sim let you feel it. Of course, good manuals. For those interested in the matter: highly recommended!
One may think if oyu have the one plane, you do not need the other. I disagree. I do not regret to have payed for both the Spit, and the SF260. Both are flying in the premier league.