I use both regularly.
OSX: better support/compatibility in the web dev ecosystem. If you need to use Sketch or build iOS stuff you have no real choice, you have to have a Mac. Downside: more expensive, need to run a VM to test IE/Edge, most people don't like the current laptop keyboards, you often need to buy a range of little apps to set things up as you really want.
Win10+WSL: generally more affordable, no need for a VM to test IE/Edge - everything is in one place, fine if you need Figma instead of Sketch. Downside: WSL is slower than a native shell (although WSL2 may well fix that), can't test Safari, tend to run into compatibility issues (usually just irritating stuff).
If all else is equal; go with the Mac. If you don't want to spend that much, you'll be ok with a Windows PC.