Michelin no longer do the 1:200000 yellow covered maps which were the staple of cycle tourist for years. They now do them by 'Department' and the scale varies from map to map, although the detail is no different. They are simply photo enlargements of the same style of map, which can be awkward to join together as nothing matches up. However the originals are still available as a road atlas, and many people use pages torn from these as an economical way of getting a lot of coverage. However this means you do have to set off with all your maps and not buy them as you go along and they can be awkward to use. This also will only do in France. The Michelin coverage of other countries is good, but often at scales smaller than 1:200000 which is not so good for cycling.
Also all Michelin maps suffer from the same draw back. Despite the fantastic quality of the cartography and the regular updates, none of them show relief by either shading or contours. The 'wiggliness' of the road, the use of green 'scenic' over print, spot heights and a good knowledge of the country's geography can all help compensate, but this is the clear advantage of the IGN maps.
So these days I think the rather shambolic coverage of the 'new' Michelin local series and the lack of relief markings has now swung the balance in favour of IGN.