I also watched the Latin American Spanish dub, and I agree that all the VAs came back and did a good job for the most part. The casting for the others wasn't bad, but I didn't see any great performance except for Carla Castañeda in a particular scene. Capper's voice was a bit too distracting for me. I only went to see that dub just because I wanted to see how they adapt the lyrics to the songs, and to contribute for ONCE to the MLP franchise. I wanted to laugh so badly when the "We've Got This Together" song ended, as the final chorus is too literal, it forgot how the rhythm in the song went, and it's just too funny to take seriously. Gosh, I'd like to relive that moment!
I had already seen the movie in English, but this time I could catch some jokes I couldn't hear well in English, and the jokes that involved puns were well adapted to the dub. I'd say the sound mixing was a bit muffled in places, like when Applejack explains that she was born in a barn and "spent most for my formative years". I couldn't understand Rainbow Dash say "Rrraised in a barn!". Fortunately it rarely happened in the film. The studio that did the editing is so far confidendential, but I can finally understand why! XD
The songs that were adapted in the film and turned out good were "I'm the Friend You Need" (though some of the lyrics need a bit of work), "One Small Thing" and "Open Up Your Eyes". The first two songs in the movie had very simple lyrics that sometimes rhymed too much, and at other times missed the rhyme. I knew the lyrics in my dub were not gonna be too good, so I just made up MY own song translations.
Overall, I definitely prefer the original dub, but I'm sure mine is not too awful. I'm glad I saw it on the big screen, and I would do so again with a *better* dub.