Which system is more easy for learning? Which one is more powerfull, has more possibilities. What Cordova can do what B4A can not? What B4A can do what Cordova can not? Which one is quicker and easier in making distributable apps. (In Google I can't find answer for B4A vs Cordova).
B4A and Cordova are very different.
Cordova is based on embedded browser (WebView) with native extensions. B4A generates Java code and compiles it.
B4A is completely native and can be extended relatively easily.
I recommend all new users to download the trial version and the beginner's guide and try for yourself.
This is just my personal opinion: i had a 15 minutes look at phonegap/cordova and b4a seemed to be easier to learn for me.
Depends on your background of course...