Unity is in an interesting position because they have a version of the product completely free. That's why they're attracting so many more members than other engines. Even jumping a user from free to paying $1 is a difficult task in itself.
Man, UE4's shader system blows Unity out of the water though. I have had so much fun playing around with it.
The reason I went with UE4 over Unity, was even if you opt for the "per-month" pricing with Unity, they charge you for a whole year up front. At that point you just might as well buy a license for the major version you're using. Plus, at $75/mo it's quite a bit more than UE4's $19. The only benefit is not having to pay royalties. For an indie like myself, 5% is chump change (because I'll be making so little). When you deal with a game making millions of dollars, you will want to start reconsidering your options. I mean $4500 times a few seats could still save you tens of thousands of dollars over a royalty.
In terms of which engine is better, that's arguable. UE4 has a steep learning curve, but it's very powerful once you dive in. I have no regrets with my purchase.