I agree the rules here seem bizarre. I originally got an NPPL SEP, flying PA38 and PA28. Then switched to microlights - the Icarus C42 and the Eurostar. Both of the microlights easily outperform a PA38, and aren't far behind a PA28 in terms of climb performance and cruise. Also, there are Group A versions of both of these planes. I've sinced upgraded to the JAR PPL.
Yet, it would seem that these 'microlight' hours don't count. Doesn't bother me - I'm not aiming at an ATPL. The rules made sense 20 years ago when microlights meant flexwings and dangerous looking bits of scaffoldpole with a 2 stroke bolted to it. But today, the gap between a modern microlight and your average basic trainer is fag paper thin TBH.
The previous poster made an interesting point about instructing. No CPL groundschool being required for microlight instructors. Having experienced both 'types' of instructor I can honestly say, at PPL level, there isn't much to choose between them - I've seen differing standards of instruction in both camps. I did hear a rumour than microlight instuctors may be allowed to instruct SEPs for the NPPL syllabus but I guess there's no truth in that?