In "JBoss, Weblogic, Websphere who cares?!?!?," Mike suggests that the commodization of Java, Enterprise Edition may not matter compared to the ability of the vendors to provide support.
For all the talk of support, ethics and good philosophy it all boils down to one thing, can you be sure the smaller of the vendors are not going to: 1) become bankrupt and not support the product, 2) change APIs and documentation every month, 3) produce certifications, and books that must be bought to operate the "open source" or "free" app server that will go out of date before you receive them.