Based on personal experiences, what, if any, Android Apps work better than the ATT Call Protect in blocking spam calls? Specifically, spoofed local numbers, if that's even possible.
For spoofed caller ID, the carriers' apps will be the best because all other apps only have access to the caller ID data.
That said, NoMoRobo.com and RoboKiller.com seem to have good followings. (I have not used either app.)
All the apps require users to report that bad calls so that the bad calls are then known to be bad.
I find that ATT Call Protect does a reasonable job but is far from perfect.