I had a TDI and sold it back to VW and got the e-tron. I love the e-tron, but on long trips I've never come close to my mpg that my TDI got. My wife also has a TDI and she had hers "fixed" by VW instead of selling it back, and even now, it still beats my e-tron by 5-7 mpg.
Where my e-tron kills the TDI is around town, due to the battery. I drive around town most of the time and charge at home, and I'll go 2-3 months (or sometimes longer due to working from home) between fill ups.
I like driving my e-tron on long trips, but just accept that it will cost me a little more in fuel. I drive like a bat outta hell and get ~35mpg. My TDI got close to 40. My wife gets close to 45mpg.