I believe written language is a much more important invention than the internet. Without written language, humans wouldn't be able to code things on the internet. Internet maybe cool but lots of the things on the internet have to do with written language. "Speech is human nature itself, with none of the artificiality of written language." We can talk a lot using written language too.
I take the point of con in that I think the whole idea of comparing the two in such a manner is ludicrous.
You're right that the internet can't exist without written language, because written language is how almost all communication is performed on the internet. Why, then, do they need to be compared? Why do you need to say that written language is better than the internet?
Since no one could rationally or logically take the stance that the internet is more important than written language, I will instead take the stance that this debate topic is fallacious and ludicrous.