Hi, I’m reviving this thread since I’m currently playing the Rebuilt version, too.
I watched some YouTube videos of the Alpha and Beta version for comparison - in particular, Ga-Koro seems to have looked quite different - but overall, I was counting on the Rebuilt version being more stable.
It still crashes fairly frequently, but at least I don’t have to worry about the game not being saved (using the “debug menu” at the start, from which you can jump into any Toa’s level), or such things as accidentally continuing with the former Toa into the level of the next one.
Spoiler up to Level 2:
(I saw one Let’s Play where somehow, Onua remained the player character after his level, instead of changing to Gali. The player thus walked into Ga-Koro as Onua, yet all the Matoran were addressing him as Gali. 
Doesn’t really change that much, I guess, because becoming Gali doesn’t automatically give you access to the Kaukau, actually. I wonder if Onua kept his grappling hook, though, since that is something you have to find for every Toa anew.
One kind of silly question:
I’ve heard that the original developers at Saffire put some rather infantile humour into the game in form of three little “gimmicks”:
- Onua could “flip the Gukko bird” to the camera with the middle finger of his claws
- Pohatu could… eh… water the cactuses in the deserts of Po-Wahi
- Tahu could… mmh… release methane out of his Slot B over his flame sword, igniting the gas in the process
Does anyone know how to do that in-game, and is it still part of the Rebuilt version? I’m currently playing Tahu’s level, and that “fire fart” seems like a particularly useful attack, if it can actually be used to do any damage… 