The anime and manga are done by totally different teams >_>
If you drop either, the other would be unaffected, except for unpredictable economic and popularity issues.
I wonder. If they're done by 2 different teams, there should be 2 different story writers/writing teams, but most likely there's not. But let's say that it's correct and you drop the manga, then the anime could suffer badly, due to not having a good story. Now there could of course be a whole lot of discussion about this, changing slight aspects of the above, but let's not. xD Because then my flame war sense would start to tingle and I'd have to hop out of bed to save the post... o_o;