They're pretty similar apps in terms of features (Aegis does all of that too).

Personally, comparing screenshots, I think Aegis' interface and choice of colours is more sleek, especially in dark and OLED modes, so it got my pick.

andOTP used to have some pretty bad issues with security. I switched from andOTP over to Aegis way back then; I've heard that the andOTP author has been extremely active & responsive since, and responded/fixed the aforementioned issues over time, but I've been so happy with Aegis that I haven't felt compelled to go back.