The only substantial difference between Amazon Linux and CentOS is that Amazon Linux has its own RPM repos (hosted by Amazon) so you may find that versions of software that are available in CentOS are not available in Amazon Linux. This isn't that frequent that it would cause a problem for standard usage situations.
On the other hand, Amazon Linux is designed to be used with AWS, so it includes things like the AWS client utility, which is one less thing to worry about if you need your servers to interact with the AWS API (eg if you were copying data to S3).
Another thing to consider in terms of using Amazon Linux is that every time you start a server with Amazon Linux the server will automatically install any outstanding security RPMs for that distributions. There is very handy if you have dynamic infrastructure in which you are starting/stopping instances every day, or use autoscaling extensively.
For me, the best thing about Amazon Linux is that it comes with very little installed on the OS other than the basic utilities required to connect to it. From that point of view, you don't need to worry about uninstalling things like Web Servers, SMB daemons, printing services etc and instead can just install the precise set of packages you require.
If you are really worried about support, you can pay $49 per month for developer level support, from which you will get answers to your questions with 24 hours.