It's very difficult to have acceptable startup times with NS+Angular in Android. It's not uncommon to see apps taking 6 sec or more to start AFTER having been optimized with Webpack (mandatory!). The same app in iOS takes only 2-3 sec. Also, this seems to happen only with the NS+Angular flavour. People using plain NS (without Angular) don't seem to have the issue.
Ionic Framework is currently one of the most popular frameworks for hybrid mobile app development. This has resulted in a very large community of active users who contribute to the community by writing tutorials and answering questions.
Ionic is still a young framework (version 1.0 was released in May 2015). There are still some quirks and bugs in the framework to work out, which you can see a list of on their Github.
However Ionic is under active development and bugs are generally addressed quickly.
Despite being such a young framework (early 2015), the support for React Native grew quickly. There is a forum, active tag on Stackoverflow and many other ways to get help from the community.
Whenever there's functionality you need that they don't use in their apps, it's not going to get developed by them, even if it's obvious it should be in the core. They always say to either submit a PR or create a separate module.
React Native is not the most beginner-friendly framework for creating mobile apps with JavaScript. It requires that the developer know React, which is known to have a steep learning curve.