It's better than a REPL, that allows you to write a game completely live. I'm not sure what you think is lost since you didn't back up what you are saying with anything.

It is strictly less powerful than a REPL. Claiming that you can't live code a game at a REPL is false, because I do it on a regular basis. When I write games in Scheme, I use a REPL to write the game live, doing all of my editing within Emacs. I do not have to save files for the code to be evaluated, I just press a keystroke to evaluate the specific form I'm interested in. I can evaluate more fine-grained sections of code, not only entire files.

Pressing a keystroke is all it takes to save a file.

Also if you are selectively executing parts of files, how is it that you are editing the live running source code?