It's not so much a question of comparing performance or effort so much as directorial choices in Let the Right One In vs Let Me In.
I didn't think the directorial choice revealing Håkan as a pedophile and his arrangement with Eli (which was in the book) was necessary in the American adaptation. The Swedish version edited it out of the adaptation because it would have begged so many more questions and character development in the relationship between the vampire and its taker that it would not have been feasible in a feature film.
The other obvious comparison was the pool scene where the Swedish version didn't feel it necessary to go for the gore...just showed the repercussions and let your imagination work.
These un-necessary additions to an otherwise vanilla adaptation in New Mexico (at least Stockholm has a period of the year where a day of night is possible) is what made the entire film redundant especially since the American version came out so soon after the original.
While the performances are strong in each film with the talent assembled, I just felt it was on par with taking Hamlet and having it take place in Seattle for no other reason than to make it American vs making an American interpretation.