The reality seems to be that the test audience reacted so negatively to JL, a sort of, "Three strikes. You're out. We're done with this franchise" attitude that WB panicked and felt something had to be done but with a relatively minimal budget. Since they rushed to get to JL way before they should have, they also rushed to salvage it. Bringing Whedon in was done specifically to change it, especially the overall emotional atmosphere of it. But no way were they remaking the whole movie.
The reality is probably that, if you loved MoS and B v S, you'll love the Snyder cut of JL. If you hated the previous two, you'll hate this. If you are in between, which I am, you'll probably think Snyder's JL is okay but nothing big.
I honestly want to see it if only to know which I think is better and which I like more. I suspect I'll think Snyder's version is better because it won't be disjointed. It will fit with Mos and B v S and even with itself. I may end up viscerally liking Whedon's version better.