Looking on where Microsoft is going with asp.NET vNext I would strongly encourage you to use MVC for any new development. Though asp.NET vNext is still in an early phase, it seems that the main effort will be put into improving MVC while web forms will be supported for backwards compability in some environments (but not all, like the new cloud optimized version). Therefore, going with MVC clearly reduces the risc of a rewrite within a few years.

I agree with Linus and there are also a lot more help and examples in MVC than in webforms even for EPiServer now.

There are a little barrier to get over to understand the filosofy of MVC but I think all of your developers will get over it and understand it in a short time. 

We are not doing any webforms at all apart from maintenance of old sites and when looking back in a web form site after working a while with mvc you will wounder how you could stand working like that :-)

Good luck

This blogpost from Scott Hanselmann is explaning a lot.. http://www.hanselman.com/blog/thefutureofnetontheserveraspnetvnextcontentandvideosfromteched2014.aspx

Agree with Linus but also worth mentioning that a website change from time to time and in 2-4 years you have probably built a new website, with probably vnext v2 :). Therefore I would still sugest you choose what ever you like. Also MVC and building complex datadriven websites tend to be troublesome.

There is also a Community Standup worh following on youtube: https://www.youtube.com/watch?v=NgbA2BxNweE&list=PL0M0zPgJ3HSftTAAHttA3JQU4vOjXFquF