JetBrains' advantage is that they have full integration and better understanding of your code. WebStorm works better with TypeScript than even Microsoft's own creation. This all translates into AI performance

Have you actually given them a real test yet - either Junie or even the baseline chat?

Junie is good. Needs a few UI tweaks, but the code it generates is state of the art.

I wouldn't underestimate Eclipse user statistics. That may sound insane in 2025, but I've seen a lot of heavily customized eclipse editors still kicking around for vendor specific systems, setting aside that Java is still a pretty large language in its own right.