The Spitfire VIII and XVI are both LF Spits meaning their Merlins were rated for medium to low alt. Our Spitfire IX is an F IX meaning the Merlin was rated for medium to high alt.
If the Spit IX we had was an LF IX I'd say the IX would be preferable to the VIII but with the VIII being an LF version it's a better bet in terms of performance and the extra fuel in the wing tanks doesn't hurt.
Remember when you are in an XVIe you are in a bird that is exactly the same as an LFIXe outside of the Merlin being a Packard produced Merlin 266 vs the Rolls Merlin 66. Same performance, came off the same production lines. Only way to tell them apart is the serial number
As for 'classic" Spits. Jeffrey Quill, Supermarine test pilot considered the VIII the best of the Merlin Spits. The IX, although the number was after VIII was really an interim version. As production continued it got the updates the VIII had for the most part. The VIII was specific for overseas use too so it was 'tropicalized' while the IX and XVI were for "Home use only" meaning the ETO.