http://unity3d.com/unity/licenses
I can learn from crippled free version, but eventually I'll be running into things stating "you need the pro version features for this, this, and that".
With UE4, $19 got me full engine to mess around with.
The free version contains nearly everything you could ever realistically want to do. And some of the "pro" features can easily be written into the engine manually. The only hard and fast licensing requirement is the sub-100k revenue requirement. Up until then, Unity is about as free as it gets.
Except publish to something other than desktop windows - or has that changed?
Major restrictions are no render to texture and a Unity splash screen on the app boot.
I suspect html5 will be supported in free Unity 5.0 (it is in the pro version currently in beta).
This wasn't obvious from their site.
There is also a free 30-day trial. That should be long enough for you to realize if you want it or not.
https://answers.unrealengine.com/questions/15056/need-some-c...