I was about to say pretty much the same as B4aeros, were it not for the fact that he can type faster than me !
It looks to me as though either route will probably take the same mount of time and the same amount of money. On that basis the NPPL(SLMG) to EASA(TMG) route looks the more promising, as you have the option of upgrading when/if funds or interests allow.
By comparison, the microlight route seems as though it will be a bit of a dead end if you want to go further from the point of view of licencing. However it must be said that there are far more microlight schools, clubs and aircraft than there are SLMG/TMG facilities. It is also true that some pilots are 'downsizing' to microlights due to cost or because of the less rigourous medical requirements. Some of the modern microlights are very sophisticated and comfortably outperform the standard light aircraft.
Finally, doing the exams before the course is an excellent idea - it would also be wise to have passed an appropriate medical before spending all that cash on flying - presumably the medical for a Nigerian PPL would suffice.
I would suggest that you have a trial lesson in a microlight and an SLMG or light aircraft if you can - that should help you decide.
Best of luck
