I tend to only upgrade when i need to, meaning I needed the card with the best longevity. So for me, the 390 was an easy choice. If I were planning to replace the card in a year, I'm not sure what I would have chosen as both perform about the same and I don't use or care about nVidia's software.
Basically, either is fine if you plan to upgrade again soon, otherwise go for the 390, but a 390 with a good aftermarket cooler.