Hello. I have not used either of them, but already I do not want to experiment with a trailer. Here are the reasons:

it brings extra chances of a punctured tires.
it gets too much attention and probably someone will want to look into it.
the dynamics and handling of the bike will be worse. IMHO.
The trailer is something that is hard to make on your own, while bags even in Africa are bags... Cheap and replaceable.

The advantage of the trailer is probably the capability of carrying more and bigg luggage. It is easy to arrange things nicely...

So, it's an alternitive, but I personally wouldn't use one on my long cross country tour.
Good luck with your either choice.

P.S. Most serious bikes just use panneries. Why?...
I only saw two of them with a trailer... kind of ritch kids..