I'm also really interested in this question!
So far for me B4A is by far the best option.
I tried Appcelerator Titanium about a year ago, as I read very good critics after some research in some forums.
A simple Hello World was 15mb! That was absolutly a decision killer, for me was unacceptable as I was planning
to target some hispanic public (mosly south america, ie 3rd world countries) in which having a Samsung Galaxy Y
and similar phones was really common, and the low internal storage capacity is a really big problem, so every MB counts!
The IDE was ok, the main language is Javascript, the community is about 600k people but I didn't get into it, so I don't
know if the have really Smart/knows-how-to-solve-every-single-problem/Alien people like Erel over here.
Then I wanted to do some cross platform gaming. I tried Stencyl as it seemed to be really easy to use. Indeed was very easy
but the result was not really smooth. There was a flappy bird example and you could feel the little delay between you finger
tapping the screen, and the bird going up and the sound.
I also tried Marmalade in august from 2013, they were introducing by that time the Lua scripting language. It was promising
but was very new and not mature enough (you can still use C++ which was indeed very mature, but it takes away the Rapid Development
idea, which was why they introduced Lua). Marmalade uses C++ under the hood and is based in Cocos2d. I didn't stick to it as
it was expensive. They now have some more afordable prices, and also a free version which put ads at the beggining of your game.
Maybe its time to give another eye to it. Its also cross platform which is very good.
I never tried Unity, but its one of the more powerful game engines. And it seems to be they are doing a good job in the mobile world.
Some of the Angry Birds from Rovio games were made with Unity. They have a free version for Android with some limitations, and
the complete version is $1500/Year which I found extremely expensive, and I dont want to risk lot of time learning a new platform
using the free version, just to see that I can't complete some stuff because I don't have the complete version.
Then of course, I also tried the native way: Java + Eclipse. Java is not hard to learn if you have some OOP knowlede, but I found
that the ADT is a real mess. You have oficial examples that don't compile, from time to time if you update ADT, you break eclipse.
Doing simple stuff takes lot of lines of codes, which in B4A you can do with just about 1/5 of what you would write in Java. I think
that if you ever tried to develop in Java, you will apreciate the real work and beauty of B4A, everything is just so amazingly easy!
Android Studio is just an IDE, it tries to replace Eclipse, you still use Java. For me, the IDE crashed twice in Ubuntu, just unacceptable.
Its still in a beta, so there is time to improve I guess. But they introduced compile tools like Gradle. I know that this kind of things should
help, but come on! A compile tool? What is that? Do you eat that? I'm struggling just to make things work and now I have one more
think to take care? Are you even trying to make life easier for developers?
For me, now that B4i was introduced, there is one more reason to stick to B4x family for a long time!