The creators of Cordova, have been bought by Adobe, and continue development of the original platform and add-ons, therefore, all the advantages of Cordova apply to Phonegap.
Adobe adds to Cordova a practical desktop application to organize development and a cloud platform for building on different platforms. Customers, do not need to have an up to date compiler chain for every platform on which they need to create a client.
Phonegap has a generic client that speeds up development time by not requiring compilation for testing apps on a device.
Adobe, also offers professional support for Phonegap, as a plus.
For everything else, regarding the advantages of the platform, see Cordova.
As with Cordova, be sure to check that all application requirements are covered by the standard features of the product.
Extending native functionality requires deep skills and defies the purpose of simplicity.