If you use puppet/chef for the whole stack, you gain the ability of just starting a new machine and in a couple of minutes having it configured in the exact same way as all the others.
With fabric and similar systems it's a bit harder. Basically you'd have to write your scripts exactly the same way you'd write a puppet/chef recipe: "make sure this is configured that way, make sure that is installed", etc. (or do migration steps) It's very different from fabric's "do this, do that" approach. Unless you run fabric on every single host after you make every change, some of your infrastructure will be lagging behind.
For example, what do you do when you create a new server, or do an upgrade that involves different dependencies? Run a fabric script that migrates from state X to Y? What happens to new machines then? How do you make sure they're in the same state?
I found chef a very good solution even if I have a single server to manage. No need to think about how it was configured before. Migrating to another provider? Just migrate the data, point the server at chef, done.
With fabric and similar systems it's a bit harder. Basically you'd have to write your scripts exactly the same way you'd write a puppet/chef recipe: "make sure this is configured that way, make sure that is installed", etc. (or do migration steps) It's very different from fabric's "do this, do that" approach. Unless you run fabric on every single host after you make every change, some of your infrastructure will be lagging behind.
For example, what do you do when you create a new server, or do an upgrade that involves different dependencies? Run a fabric script that migrates from state X to Y? What happens to new machines then? How do you make sure they're in the same state?
I found chef a very good solution even if I have a single server to manage. No need to think about how it was configured before. Migrating to another provider? Just migrate the data, point the server at chef, done.