If you are "investing" because you want to sell some of it when it gets discontinued, probably Kodak would be a first buying choice, followed by Fuji. It makes little sense to buy something you have no interest in using though.
If you like Ilford film, there is nothing wrong with putting some in the freezer to hedge against price increases, though it's not likely as volatile as Kodak.
I bought a bunch of Kodak 8x10 film and it's gone up 30% in cost in less than two years. At some point, the price increases, if Kodak is not careful, will drive people away and a film might end up discontinued. If it's anything cult like or hallowed like some of the polaroid products, it may maintain a good new-old-stock value. I bought it to use and bought enough due to the uncertainty of Kodak's future.