The Buchon has a licence built Merlin 500/45 of 1,600 hp.
With those 1,600 hp the Buchon is a 413 mph bird, which is similar to a Merlin 66, 1,720 hp Spitfire LF Mk IX (or the Spit16 in AH). Rate of climb for the Buchon is about 5,500 fpm. This leads me to believe that the Buchon is lighter than a 109G but somewhat more draggy. That engine installation is particularly ugly from an aerodynamic viewpoint.
The 109s are smaller and has less wing surface, and are lighter than contemporary Spitfires. Less drag = more speed at the same power. Less weight = better climb at the same power.
These two birds have almost the same power. The 109K has 54 hp more. You can also see that the DB 605DB has a slightly higher full pressure height than the Merlin 266, but they're close enough for comparison. They are about equal in weight so they have very similar climb rates.