Please suggest which App Server is most preferred and which one is least preferred?
It could be based on various parameters like performance or stability.
Outside AEM , in general my understanding is that Tomcat is not preferred for heavy traffic production installations, as its performance degrades with volume of info.
One reason for choosing an App Server is usually down to the customer already having the app server in their estate, and a mandatory requirement to deploy all applications in their chosen App Server. Another reason is if you wish to use a specific feature available in an App Server that is not available in AEM. For example HTTP session failover/replication across a cluster.
The vast majority of customers use the standalone jar to deploy AEM.
We used to run AEM inside WAS (IBM Websphere Application Server) because as a company we use a lot of IBM products and that is just the way things went, however we have since moved to just run AEM standalone using its in built CQSE servlet engine and have seen 0 impact to performance and it has saved us license fees/support costs of also having people spending time to look after the WAS servers.
So personally I'd recommend unless you have a really really good argument or some annoying policy of always using app server X then just run it standalone.
I think these are highly valid points in this discussion and will cover 99% of the use cases.
But given a scenario, customer wants us to use any App Server for AEM, wherein even the selection of an App Server is also in our bucket, how to choose one?
Does Adobe have any recommendation?
Definitely Tomcat's scalability issue (if still exists in the latest versions) weighs against it.
