Pros & Cons of Unity vs Unreal Engine 4 vs building from scratch with cardboard

Unity:
Pros:
-less dev time from engine
-Royalty free

Cons:
-without a monthy fee we cannot leagaly earn more than $100k
-Unity with cardboard is only in beta (more bugs?)

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UE4: < Sam's preference
Pros:
-less dev time from engine
-no revenue capacity
-supports Vulkan

cons:
-5% royalty after the first $3k earnings (seems fare)

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scratch:
Pros:
-no legal contract (no royalties)
-ability to use any tech (such as vulkan)

cons:
-it will take a long time to dev
-will be hard to make universal
-will have a lot more bugs