I would focus on the cost issue. If they are going to be using Websphere, then they will need to use VAJ Enterprise Edition. VAJ EE is $2800 per developer (site licenses or government discounts would make it less). WAS Advanced Edition is $10,000+ depending on how many processors are involved.

BTW, there are some non-development issues in regards to using WAS. One of the really nice administrative features is cloning. With minimal effort, an administrator can clone a server onto another server and have the two machines be load balanced.