[Nyororin]

9 times out of 10, the only reason I`m watching the anime in the first place is because I`ve already read the manga and was interested enough to do so...

So it becomes a moot point, as the manga is almost always very far along by the time it gains enough popularity to be made into an anime.

There are only a few that have gone the other way around for me, namely Nodame, but even then I would have picked up the manga and read it first. But I watched it as a re-run marathon thing over 3 days so didn`t get the chance.