First of all, btop is included in the default repos of most Linux distros, so you don't need to worry about security. This also applies to htop and glances by the way.

In terms of tangible feature benefits, btop also offers disk I/O stats, network throughput stats, partition usage, and even GPU usage (if your distro compiled it with GPU support).

In terms of "nice" stuff that's non-essential, the overall UI is a lot more user-friendly and in many ways, better (subjectively). Eg there are visual graphs for various metrics, you can filter process names by substring, get detailed stats of a specific process, see the tree view of all the processes, easily show/hide various parts of the UI (eg you can focus solely on the process list if that's the only thing you're interested in).

There are also some distinct advantages the UI offers easier to send specific signals to processes. Eg in btop I can just select SIGSTOP from the menu, whereas in top, I'd need to remember or lookup the numeric equivalent (eg 19 for SIGSTOP).

Other top alternatives also offer similar feature sets. Glances also shows the most recent warning/errors from the system logs), as well as container resource usage which would be handy for some folks.