One thing I have seen Simplify3D do well is supports. They are very easy to cleanly remove and the default options generate enough support without going overboard. It also allows for custom supports, which can be handy. You can also set a number of options based on the layer you’re on. That can be handy for adjusting things on some prints.
That’s not to say it’s the end-all for slicers. It has issues just like every program. It’s also a bit pricey for what it is, IMO, but I do like it and the interface.
If you haven’t hit issues in Cura, keep right on using it. It works great for most things and generally results in good quality prints. There are some other programs like Simplify and Slicer that do a better job with some things, but Cura does a very nice job most of the time. And really, some of the people that like one over another just like the user interface better. Generally, I think Simplify is more “pretty” and has a cleaner layout than Cura. I wouldn’t recommend buying it based on that alone, but it’s a nice extra.