I plan to build a mobile application on all platforms which serves up results based on the location of the user.
I have checked the following: phonegap,bootstrap,appgyver,ionic.
Definitely go with PhoneGap.
These have been around for decades and you can find all sorts of tutorials, sample code, discussion, and frameworks.
What framework you use depends on your experience and knowledge of the corresponding programming language. I would also recommend looking into Xamarin, which allows you to create native applications for all platforms while writing code in C#
I would be happy to discuss further if you would like to jump on a call.
Phonegap is sweet - however, I think the bigger question is - how involved with the framework do you want to be? How senior will your development team be? Maybe this team is an army of one? You?
While you are open to ideas, why not look at some of the game engines that use a development platform with data integration capabilities?
Ionic Framework would be my No.1 choice!
Appgyver just came out with upgrade, you should check it out!
But Ionic Framework rocks!