I have owned gear from both companies, they will both work well with the right equipment. The ARC will be more revealing, it is the most resolving tube gear I have ever heard. That said, some find it a bit too light for their tastes. The VAC is also highly resolving, but not quite so much as the ARC. The VAC gear will have just a hint of tube sweetness. I must admit that I prefer the sound of the VAC gear.
I agree with Jwm, I would not worry about the long term future of an audio company, tube circuits are fairly easy to find a good repair-person for. Many tube circuits have been around for many decades, just using different tubes and faceplates, while much of the circuit remains unchanged.