Definitely the effort will be lesser than native app, if you are familiar with web technologies. You have to compromise on performance, if you choose Ionic framework.

If you are familiar with react, then checkout React native.

I think this depends on whether you're familiar with making native Android/iOS apps already, and whether you're also familiar with making Angular apps.

I don't have a large amount of experience making native Android apps (and absolutely no experience making native iOS apps...), but I've used Ionic 1, and being even vaguely familiar with Angular at the time, it was pretty easy to get things working. :)

Plus if you plan on making an app for both Android and iOS your Ionic app should run on both with little to no issue, so you save yourself having to port your code over from one to the other.