No, there's not really any additional benefit to owning both if you're already buying IDEA. WebStorm's features are essentially a subset of IDEA's. They have

No, there's not really any additional benefit to owning both if you're already buying IDEA. WebStorm's features are essentially a subset of IDEA's. They have a slightly different release schedule (WebStorm seems to be more frequent), but everything that gets added to WebStorm ends up in IDEA reasonably quickly.