User blog comment:Cristina7/Introducing Discussions, a New Platform For Engaging Your Community/@comment-5275700-20161001024821/@comment-5275700-20161003191222

Bug reports from Special:Contact and from within the apps end up in the same place. Both web form and the app form give us some data about the hardware and software used by the reporter, to help with some initial diagnosis.

It's fine to use whichever method makes the most sense for you, regardless of what you are reporting. In any case, please give as much detail as you can about the bug or security issue. Browser version and app version are important things to note.