I actually recently heard an interview with Feargus Urquhart from Obsidian on the game informer podcast and from a technical perspective he seemed pretty positive about Bethesda toolset and also had the opinion that one of the reasons they keep it going is because not only is it great for them since they know it so well but also because they want to keep modding open to as many of their fans as possible.
I heard no such thing. I heard a developer being diplomatic and evenhanded to all the engines they have to work with. He isn't in a position to embarrass other developers on their technology.