The three major factors I would rank the IDEA over VS.
1. Extensibility, its more likely to support X language
2. Crossplatform, it actually runs on my platform
3. Its UI doesn't change drastically every few years. This is such an underrated thing IMO. Neither VS or IDEA are pretty IDEs, they both are actually butt ugly. They don't need to be. But VS goes thru so many visual changes and reorganizations, its the same reason why I don't use Office. I'm not sure many ppl view this as a bad thing however. I often find MS fans loving to brag about how "modern" their software always looks, even if it still looks just as shitty as the old one lol.