Try both and see which you prefer, they are free after all.
Boy, what a loaded question...but a good one. What would be nice, would be to take the best of both and come up with a single one, but I don't guess that is going to happen. I notice that, for example, on Droidplanner, I lose a LOT of functionality when I try to use DP on my Galaxy S3 that I don't lose on my Asus tablet. On my phone, I can't enter any waypoints, which makes it pretty useless other than for the HUD. However, I like that the copter icon shows the orientation of the copter and I like the HUD on DP better. If the waypoints worked on my phone, I'd probably use DP. If the HUD was more full-featured in AP and the copter orientation showed, I'd probably use AP.
What this answer DOESN'T reflect, is my sincere appreciation to both developers. I don't know how the GCS "war" will work itself out, but we, as end users, will be the benefactors and owe a great debt of gratitude to all who are participating in the development. I, for one, do not take any of what you guys are doing, for granted. Thank you muches.
Agreed with the two above.
At the moment they both have their own advantages but so far the best GCS I've seen is by DJI for the iOS. Very simple to use interface and still very functional, I'd like to see both Andropilot and DroidPlanner get to this stage and as Rob says, combine the best of both.
Droidplanner 2 is in testing and looks great, I also use Andropilot frequently as I am used to it. There is no GCS war.