Worth mentioning that in this brave new NPPL world you can do one license and add SEP, microlight, SLMG (and glider?) ratings fairly inexpensively - probably clocking all of them up for the cost of a single PPL(H).
Microlights have a single major advantage over the rest, you've a fighting chance of affording one all to yourself. SEP will always get there faster than anything else, Rotary will allow you the ability to land in pub gardens (but only the pax can drink anyway !) but you'll get less hours to the pound than anything else. Gliding will cost similar to microlights but also absorb you in spending all day "mucking in" with dozens of other aviators.
At the end of the day, they're all superb fun - the decision is a combination of aesthetic and financial, and nobody but you knows how you stand there.
So long as you can afford it, I doubt you'll make a bad decision.
G