A better OS stack, where devs are busy moving beyond C, has better asynchronous IO stack, kernel level thread pools, embraces a mixed architecture with separated kernel and personalities, driver crashes don't bring the OS down, embraced by the games and graphics communities, allows for multi-GPU usage ....
Hardware support + you can run the Adobe suites, Microsoft Office, etc.?
I think WSL will be very successful among developers. You can just get any laptop from the store that runs Windows 10 and have Linux running at native speed (except I/O, which is currently a bottleneck in WSL) at the same time without the hardware compatibility problems, etc.
:P