The Heller kit is indeed a "Heller original" that shares the hull with "Couronne" - but only the lower portion, from the upper gundeck upwards this is a different kit!
I don´t have any problems with this because "Couronne" as the first real big warship of French design was most likely based on the lines of the "imported" Saint Louis that was built in the Netherlands.
The Heller kit has more parts than the Airfix one, with full guns on every deck. The heller ship is a bit wider and shallower in height than the Airfix ship, the stern ornament is -from what I have read, correctly- in fact just a cut-out-paper part that has to be glued onto a blank piece of plastic -the original is said to have been a painting!- while the Airfix kit carries real ornaments.
Overall, the Airfix kit looks a little more elegant but I like both kits - all in all there are not that many differences, while the Pyro kit is way overdone in its too pronounced lines (like the various HECEBOP kits of the Couronne BTW) and has a -to put it politely- "ornamental" looking wood grain structure.
There is one bigger flaw in the Heller version: all the lower hull planks are parallel to the waterline and they do not become narrower to the front and stern ends - that´s not the way a ship is built, just easier to engrave!. A real pity and I do not know ANY other Heller ship kit that has the same issue, maybe at the time the molds had to be finished the guy who knew how to build ships was on holiday....