The question of instances vs dedicated servers really depends on your business and how you charge your customers.
If you’re more of a custom shop and build more complex sites, you may want to use instances because then you don’t need to worry about server resources and how to allocated them to a particular site.
But if you’re more of a volume shop, offering a more standardized service, you may be able to pack more sites per server, lowering your cost per site.
We can help with the math and work out what is best for you, so just reach out and ask!