A thought or two.
(1) Basically the only thing close to a European consensus about microlights is the definition (and that is still a bit tenuous). CAP804 applies to the UK only in this regard, and any other country will have its own rules.
(2) P92 versus C172. Both are perfectly good safe flying machines, but the speeds and attitudes are somewhat different - a shorthouse like me can actually see over the P92 instrument panel for a start. The Technam will need about a quarter of the runway to take-off or land that the C172 does, will have a similar climb rate, then be slightly slower in the cruise. To land, microlights bleed speed off much quicker, and hence need a somewhat different style in the approach and landing to a heavier aeroplane like the Cessna. Basic airmanship and the fun of flying don't change of course, but conversion training in both directions, regardless of legalities, is a survival necessity.
(3) As a general rule, assume differences training when going down in weight, and a skill test when going up.
G