Well old boy, the Airfix kit is the MkIII, with Hercules radial engines and longer wing span, and the kit is around fifty years old. That said, it was quite advanced for it's time but, by today's standards, is quite basic. The surface is covered in rivets which, surprisingly, on my example aren't too bad, and can be lightly sanded, retaining just a ghost under paint. Overall detail again is basic but, even straight from the box, in this scale, can produce a reasonable model. Note there are no separate doors for the fuselage or wing bomb bays.
The 'Matchbox' kit is the Merlin-engined variant - shorter span, and choice of early or late fins, and again can produce a nice model. However, if you want a good Merlin Halifax, then go with the newer Revell issue - new tool, various Mark options, and, from what I've seen, a nice kit. Also the best overall Halifax kit in this scale (or any scale, come to that!).