What is the "moddable version" of Serious Sam 3?

On the very first launch of SS3, I am met with this dilemma:

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What's the difference between "Serious Sam 3: BFE" and its "moddable version"?


Solution 1:

The "moddable version" loads user mods, while picking the first option loads the vanilla game. If you've got no mods installed (as this is your first time loading it & the game is so new there aren't any), they both essentially do the same thing.

The same option was available in the second Serious Sam game, although it had its issues at launch.