I think it's important to consider that when you pay is, sometimes, as important as how much you pay. As it is now, UE4 require an initial investment of $20. Unity, if you want the full program, require an initial investment of at least $1500. More if you want the platform add-ons, and most do. From the point of view of, well me, I'd go for the $20 because I don't expect to make a penny on game making. I think I share that point of view of starting teams who have to turn every penny. No, Unity Free is simply not comparable. When people can pay $20 to get access to everything for a trivial cost, the limitations of Unity Free is non-trivial. If one can get a very good editor either through paying a full subscription or an outright license, which will amount to hundreds or thousands of pounds in contrast to getting an editor which initially will have a trivial cost but which later may be more expensive, I think most starting teams will defer the cost to later. That is, of course, also a way to lock-in those starting teams. Once you commit to this initially cheaper platform, it's going to take a lot to shift the team from it once it becomes successful.