Here are some of my personal pros and cons between the UK and U.S. versions of this film. If anybody wants to do their own "pros/cons" list, please feel free to do so! Cheers! :-)
*Pros: The voices and songs are pretty decent. My favorite characters here are Peewit (re-named William), Homnibus,
*Cons: Some scenes have inaudible dialogue, in which the characters are supposed to be talking, but somehow, the actors probably forgot to dub those parts. (Ex. the Smurfs' party sequence with Brainy giving a lecture to Greedy, the flute battle with two background ladies talking and the Smurfs cheering for Peewit, the working song with a bored Johan and Peewit briefly conversing, and a Smurf laughing at Peewit trying to cross a bridge) Also, there's no denying that some of the Smurfs during the "Personality" song number have extremely uncomfortable deep voices, notably Greedy, Grouchy, Hefty, and especially Lazy. My biggest peeve is obviously the fact that this is the only version released on DVD, which is thankfully the reason I made this project.
*Pros: Cam Clarke is awesome as Peewit; he's very mischievous, but also very lovable. All of the songs are done perfectly, notably "Peewit Wants a Smurf", "Life is a Voyage", and "Just Like Their Names". I especially love how the Smurfs' working song is half instrumental, unlike the UK version, which uses repetitive lyrics throughout the entire song. The rest of the characters are also performed very decently, notably Johan, Brainy Smurf, Matthew McCreep, and the King.
*Cons: I actually really don't have many problems here, but if I have to nitpick, I will admit that some of the Smurf voices can become pretty squawky and jarring at times. Also, I don't know why, but for some reason, they not only forgot to dub a line from the Smurf that Johan and Peewit first meet in the forest, but this dub even left out the brief music that plays when Matthew McCreep's men walk into Earl Flatbroke's castle to show the amount of money McCreep has.