Is Windows Server an easier platform to build a server on than Ubuntu?

Easy is a very personal measure. Depends highly on what you are used to or comfortable with.  Here is my opinion. As for me and most people and startups/labs/institutes i know or have worked at use ubuntu or some flavour of linux . A vast majority of servers run on linux today. Facebook , Google, Amazon, Dropbox , almost all companies that matter (from the perspective of an ordinary web user) use it as their platform of choice. What this does is that there is a vast array of software, toolkits and choices that one has while deploying a webserver. Some libraries and implementations  like Node.js, Django (python in general ), Ruby on rails have far better support and packages on this platform. It's also faster, more secure and best of all free (considering you need to keep buying additional software and licences for every new feature you wnt to add in the windows alternative , that can get really expensive. Also since it is all closed source you cannot modify any of it to suit your needs and have to rely on expensive software or tech support. YMMV