How does the NVidea GTX line up hold against the Radeon pro WX series?

I’m trying to get into UE4, wondering if anyone has used one of the Radeon Pros for UE4. I’m sitting on a GTX 1070, and leaning towards buying a 1080 ti. Would the WX be considered a better investment for creating in UE4?

Workstation cards do not perform well in game engines, there’s really very few situations where a workstation card will give a benefit–it can improve viewport performance for many objects in software like 3ds Max and Maya and there’s some specific simulation and rendering software that’s designed for it but there’s a vast majority of other programs (including games) that don’t get any benefit.
Workstation cards also are largely poor value for the performance you get and you have to spend a lot to see a difference so it’s not often worthwhile unless you have lots of money to spend. Getting the GTX 1080 Ti will definitely work better and be a better value.
However, going from the 1070 to the 1080Ti might not be that much of a difference, the 1070 is already pretty good as it is.
Since you have a pretty good GPU already you might look at the other components and see if you can upgrade other areas like faster/more RAM or upgrade the CPU. RAM and CPU will impact development for things like compiling code and baking lighting. There’s also new hardware features like Intel Optane which can make your system faster if you decide to upgrade to a new chipset.