Hmmm. After giving it a little bit of thought, I don't think I would necessarily choose one over the other. I think I would divide the money, although I'm not sure if it would be equally. Our last homework assignment was interesting in this regard... Go to a library and review specific reference material there. The library I chose to visit had all three reference books in question available, but one of them was only accessible on the web. I didn't have a problem with this, but the computerized library catalog I was using wasn't connected to the internet, and all of the internet computers were being used. That meant that I had to go home to access the material online even though I was already there at the library.
So, my first purchase would probably be more online access for patrons at the library itself. My second purchase would probably be online subscriptions, whether accessible at home or only at the library. Online subscriptions to valid information sources can get expensive, and to have them publicly accessible would be a wonderful draw to use the public library system more often (IMHO).
Of course, as a writer, I have found that my information needs can't always be fulfilled by the quick hits on the internet. And to sit down and enjoy a good book on a computer screen just doesn't work for me. Long term reading from the computer tires my eyes, personally. I would spend some money on fiction and bestsellers to fill my library shelves.
I think that quick ready reference is suitable for the internet. If I wanted to know what a train brakeman did (for example), I might first check out Wikipedia. But if I were to write about a character whose life was about working in a train yard during the Great Depression, then I would need far more information than the quick easy reference the internet provides. That's why investing in books and newspapers about that kind of detailed history would be important.
I don't think print resources are becoming obsolete. I think they are being utilized more effectively because of the introduction of electronic resources. The internet and computers allow us to pinpoint the information we need faster. They allow us to find the right direction in seeking out our reference needs. But I think that if we tried to cram all of the information that we have in books and periodicals onto the internet, the information would become abbreviated. We would lose a lot of the detail that we sometimes need, and that would be a sad loss. Again, IMHO.