What's different about this one? It looks pretty much the same

Gmail was built with the Closure library. This issue tracker is built with AngularJS v1.5.12-local+sha.7f65bbb8d.

Yeah it's unclear what Google intends with the new issue tracker. I looked it up for some issues I opened on the old issue tracker but I didn't find them on the new one, so for now it's a complete separate database.

So, are they dropping b.android.com? 
Are they keeping it? (looks that way for now at least)
So confusing. Where should I create issues?

Google has a new Issue Tracker