Aegis is open source. And it’s been around awhile and is fairly widely used, so it has gotten a degree of scrutiny.
2FAS is proprietary and fairly new.
Personally I’d rather not trust my TOTP secrets to a proprietary closed-source app from a company I’ve never heard of.
Aegis is easy to use and does everything I need. I have it set up to export an encrypted copy of the database to local storage every time I change anything. The burden is on the user to back that up outside the device in case the device becomes unavailable, but that’s not a hard thing to do.