For a starting project, why would you use Metro instead of Axis2?
What should be considred? Performace? Easiness? Tools/IDE/Plugins availability?
I wouldn't use metro, I would go either with Axis2 or with CXF (ex XFire).
I have used Axis, CXF and JAX-WS (Metro). To me Axis just feels so, out of date and wrong in many ways, so I wouldn't use that. If your application is using Spring then Apache CXF is clearly the stack you should be using. If on the other hand, you don't use Spring, then JAX-WS is they way forward. The good thing about JAX-WS is that it is included with the Java 6 runtime, thus easy to install. :)
For tools, IDE and plugins, I've been using Maven quite extensively and plugins exist for all of those WS stacks mentioned.