iOS is much, much faster at distributing updates than Android. Apple publish official numbers here: https://developer.apple.com/support/appstore/
One year after release, 92% of iOS devices are on the latest version. It only took ~3 months to reach 75%. I think it is fair to assume iOS 8 will see a similar update pace.
Compare that to Android (official numbers here: http://developer.android.com/about/dashboards/index.html) where about a year after release, only about 25% of users are on the latest version. Android L+ will be equally great with PhoneGap, but obviously if it goes at the same rate as KitKat will take much longer to reach vast-majority status. Still, it bodes well for the long term, and in the mean time we have Crosswalk which provides an excellent real browser-based platform and runs on Android 4.0+ (currently 88% of all Android devices and still increasing).
The compatibility problems and bugs in the non-browser wrappers like CocoonJS and Ejecta can be quite problematic for a lot of users. iOS 8+ will also be considerably faster with its WebGL support - possibly up to twice as fast. I think it is well worth targeting iOS 8+ / Android 4.0+ only for the vastly better compatibility and performance. You still reach the vast majority of users. The other way round you reach slightly more users, but have often severe bugs to deal with, and possibly lower performance for all users. Obviously it's everyone's choice to make themselves, but my confidence that it's a tradeoff worth making is part of the reason we deprecated CocoonJS.