I don't think this has anything to do with the treaty texts.
UK judges are known to stand up to the political establishment when parliament doesn't get their ducks in a row and very, very carefully make sure they are consistent with UK constitutional law, which does in fact provide fairly strong protections, and even more so coupled with the Human Rights Act. This to the ongoing exasperation of UK politicians. Swedish judges does not have a similar reputation.
I could very well see a UK judge deciding that extradition would not be compatible with rights guaranteed to him under UK or EU law, regardless of the treaty, due to the state of the US legal system, but I really can't imagine a Swedish judge thinking twice about it...
Maybe I'm being overly cynical, but personally I would not take my chances if Sweden if I didn't really have to if I was in his shoes.