There are 2 versions inside the main download. Specifically a v1.4 .zip file inside of main (regular) v1.3.8 .zip 

All posts discuss 1.3.8 being the newest. Which should I use for the best experience v1.3.8 or v1.4? I just find it weird there is no mention of v1.4 being the newest and it not being the main file in the main download.

I'm curious about this as well.

Came here to ask the same question, I went into the properties of the ROM in the 1.4 folder and it looks like it's identical to the one in the 1.3.8 folder, so I guess just use that one.

Yeah, I would love to get a definite answer to this, as well.