I have never used either, but from a developer point of view Telerik (makers of Sitefinity) are excellent, telerik are from Bulgaria (Bulgarians are big on programming). I cant speak highly enough of them. I have done plenty of work on Telerik MVC Controls and have been very impressed,
Sitefinityis ASP.NET, where Word press is PHP, I do know that they are looking to move sitinfinity to ASP.NET MVC, MVC is superior to ASP.NET Webforms, and far superior to php. MVC is also very SEO friendly, it has a clean separation of concerns giving very clean html, no post backs or viewstate, Already they are using the MVC Routing engine that gives full control over urls, no messy file names or parameters, you can make your URL say whatever you want, it does not have to match your folders.
If you intend to further develop your site in the future, I would go with Telerik