For me, this will always be a factor in the business side. If they see value, it's easy to sell.
If using Framework 4.5.1 (requires VS2013) will reduce server resources (See:
- ASP.NET application pauses
- Just-in-Time (JIT) performance is 15%
- “The .NET Framework 4.5 and Windows 8 have features that can help you achieve significant performance improvements for your web server workloads. This includes a reduction (up to 35%) both at launch and in the amount of memory on the web hosting sites using ASP.NET. "
)
And bandwidth resources
(CM.:
you can actually do the math and see if it makes sense. Then the developer and support side (which is pretty neat in Vs2013 - the new intellisense, nice nuget, etc.) is just a cork. From the point of view of the developer, you will also need to consider the cost of updating the application between versions, that is, the cost from 2008 to vNext against 2013 to vNext.
Update:
Since this is a very similar situation I am in, I am doing some research. Our company standards are VS2012 (RE: Microsoft Dynamics Environment).
According to “What's New in .NET Framework 4.5, 4.5.1 and 4.5.2” at http://msdn.microsoft.com/en-us/library/ms171868 (v = vs .110) .aspx they offer the following to improve your domain:
• Ability to support multiple authentication modes on one WCF endpoint when using HTTP transport and transport security.
It is always a great seller for business. See other WCF improvements at the link above.
I also found an article at http://www.msmsoftware.com/2013/8/6/the-business-benefits-of-upgrading-net-35-to-45.aspx that very specifically addresses your question. They note, as I said, better performance, better security, and increased development and support capabilities.
Your question is unique in that it is focused on the working side of things (WCF), so fluff around the best support for application stores, the best web standards, etc. somewhat pointless. I hope I have given you enough to make the answer somewhat clear.