On the whole, the Vg 33 -39 series really didn't make any great breakthroughs in performance over other contemporary designs the French had. Arsenal was proposing for many of the series the use of US Allison V-1710 series engines (eg., the same engine in the P-38, 39, 40 etc.). Obviously, this engine would have seriously limited altitude performance if it was used just as it did for the US (note: the US was not exporting turbocharging technology as was being used on the P-38).
The same engine also precluded use of an engine mounted cannon so the designs with the Allison were armed with just six 7.5mm machineguns....or seriously underarmed.
On the whole, the VG series really does not offer that much of a performance improvement over the D 520.
Now, the Bloch Mb 157 had potential. The prototype hit 440 mph and would have had 2 20mm HS cannon and 2 7.5 mm machineguns. This was real potential.