Dijkstra was correct in saying that you don't even need a computer to do "Computer Science," all you need is a pencil, paper, and a mental model of what you're trying to do given computer constraints.
Dijkstra more theoretical; Kay more hands-on.
I think BOTH are necessary, or at least important.
There is theoretical, and then there is theoretical: one is privately fueled and produces real-world industry-strong gems like Haskell; the other is publicly fueled and produces concepts such as self-stabilization and superstabilization.
If Dijkstra is so awesome someone should write a Wikipedia article with more important achievements and less medals.
I don't really understand what you mean by privately or publicly-fueled theory, but anyway...
Instead of waiting for someone to write on the wiki, you could go out there and google a bit.
Very briefly: he made major contributions to compiler and OS design (including the first Algol compiler and a whole OS, the THE OS), devised two fundamental graph algorithms (shortest path and spanning tree), and spearheaded making programming into a serious discipline rooted in maths (along the way pretty much giving birth to structured programming).
He also wrote (longhand!) over a thousand essays on CS and related topics, which are (as far as I've read, and I've read quite a few) all a joy to read.
Dijkstra was correct in saying that you don't even need a computer to do "Computer Science," all you need is a pencil, paper, and a mental model of what you're trying to do given computer constraints.
Dijkstra more theoretical; Kay more hands-on.
I think BOTH are necessary, or at least important.