Hi Armando,
The late Italeri kit has advantages/disadvantages over the Airfix one.
The main differences are:
The previously mentioned underscale outer undercarriage door problem on the Airfix kit (the italeri kit is better in this respect)
The shape of the rear fuselage is not great on the Italeri kit, although several replacement rear fuselages are available to correct it (Airframe resin is one, available from Hannants). Mind you this is an expensive and time consuming option (not to mention a bit of a faff)!
The Airfix Hawk 100 Series kit has a more accurate representation of the 7 station wing and a much better rear fuselage shape.
Replacement decals for a RAAF Mk.127 are available from either Red Roo Decals in Australia or Model Alliance in the UK (company out of business but the decals are still available out there).
http://www.hannants....product/ML72112
That sheet also has a Canadian Mk.115 option.
A SAAF Mk.120 is also available on another of the Model Alliance sheets,
http://www.hannants....product/ML72155
Seats for all are similar Martin Baker Mk.10LH models, with some differences in paint and strap colours (check references).
Personally, to get an accurate Mk.127, I'd buy the Airfix 100 Series kit and use the outer undercarriage doors from the Italeri kit as a quick fix to get the best looking option.
Cheers,
Rob