Some would argue that utdanning is about the process and that utdannelse is the result. But there is no basis for the distinction.
Once upon a time, utdannelse was dominant in bokmål, but utdanning gradually became more common. Today, utdanning is used more than utdannelse, especially in educational compositions.
Bottom line, they're interchangeable. :0)
It is also common to say in English "Pilots have long, expensive educations", i.e. making the plural educations match the plural pilots. So I tried that, and was a little surprised that it was marked correct. If I use the plural "educations", wouldn't the Norwegian need to be "lange, dyre utdanninger"?