Usually all that matters is what fad do your current programmers believe in. This is the only thing which matters and what comes after usually is rationalizing this argument.
Every webpage can be written in basically any turing complete language. I've written web services in bash, and there was a design rationale behind it.
Performance is also an issue, however, I'm yet to see a person to claim that java is just awfully slow on average sized projects sometimes (and slowness is easy: response should be around 200ms for end-user),
Ease of use and adherence to platform is also an issue, for example sometimes you feel that ASP.NET library developers have only developed libraries in their life, but never web applications.
Noone will ever claim that as they either believe in a language, and know it, or don't believe, and don't know it. I'm over with believing in technologies, and maybe the projects have moved on (I won't ever write a web application in java 1.4 again for sure, and I hope postback was killed by now)
The java community seriously believed for years that J2EE 1.4 is suitable for web application development. Today, Spring is much closer to Ruby on Rails or PHP than it is to J2EE. The .NET community seriously believed that postback is a good idea. It was a usability disaster, able to make planets extinct.
We all know that these were brain-dead ideas, the communities have moved on. We have new brain-dead ideas and a huge bunch of people claiming it's the way to do it.
It doesn't matter. Keep the cognitive time limits, ensure that the user interface is responsive, and do whatever your coders feel fine with it.
- Have a list of what technologies your current coders know on a whiteboard,
- Give everyone 5 sticks, and ask them to place it wherever they see it fit.
- Grab the top two or three, form teams and ask them to create prototype
- Walk through each prototype in a code review session
- Make a decision.