I purchased the UT3 Collector’s Edition and have all of the UT3 editor tutorials that came with it on DVD. How different is map creation in UE4 from the UT3 Editor? I’m thinking about going through the UT3 Editor tutorials to get back up to speed before doing a one-time UE4 purchase (preferably the latest possible version). I’m wondering if learning how to map for UT3 would be worthwhile or a waste of time.
Take a look at some UE4 level design tutorials: ?v=XDsJOFyxMnw You can find them on the official unreal engine channel
I never used the UT3 editor before, but when it’s like UDK/UE3 then it’s pretty useful when you watch the UT3 tutorials, because not so much have changed and it will be easier for you to switch to the UE4 
Things like lighting are all new, but most other basic things are very similar. It is just a different interface and some different properties and features left and right.
I would prolly just get ue4 right away and use ue4 tutorials though. More efficient.
It’s build on UE3, some features are completely removed, like subtractive levels. But mostly there’s just a new interface and some other new options.
Its quite easy to adapt to, somethings are new, but honestly its almost exactly the same as UE3. Best of luck!