Unity is good for learning and quickly prototyping, but it's poor for professional development.
If you're not a hobbyist and you're serious, invest in Unreal 4 when you can.
Here's how I compared the two to my friend.
Unity is easy to get into, but hard to make a final, finished product with.
Unreal is harder to get into, but easier to make a final, finished product with.
But Unity is still a VERY viable option for a serious game engine, it just tends to take more tweaking to get it to where you want.