[bob1029]

> You need to test the gameplay concept as cheaply as possible.

There are some edge case concepts that I have found to be completely impenetrable on commercial engines.

Multiplayer is the #1 thing in my mind. I've gotten the FPS multiplayer examples to "work" for UE and Unity, but the confidence I have in these solutions is not great. I've seen what Unity can do (BattleBit), but I don't know how many decades of game industry black magic and hackarounds it requires to force a commercial engine to behave that well.

I really think the answer is that it depends. If you aren't trying to have a "perfect" version of some gameplay aspect (i.e. multiplayer in my case), then the commercial engines will absolutely be the fastest path to validating your idea. Put differently, I think some game ideas are not possible to validate on commercial engines. But, I don't think this is very common.