As someone that has used both UE and Unity, Unity is far more restrictive in its free state (no soft shadows, forced Unity splash screen, no level of detail support, no inverse kinematics for animations, no profiler, and many more).
Also the Pro license for Unity is pretty expensive up front -- a few hundred for Pro and then another $100-200 for iPhone, another $200 for Android, etc and thats per month (or $4500 one-time payment for desktop + iOS/Android) regardless of how much you make with your game.