Spaces is a good feature. Topics is the worst thing I've been subjected to in my life. I have a second account in Japanese and Topics constantly adds posts about trashy American pop stars I barely know to the feed.
The main diff though is that Twitter for a moment in time started taking some shots. Not that they were all the best shots. But for my first two years there it felt like the company took nearly 0 shots. That shift happened with Kayvon.