I watched the second episode of the SyFy version, and the first episode of the second season of the BBC version. And I think I caught the major problem.
The BBC show is serious, but there's a whole lot of comedy packed into it (largely thanks to George). This became strikingly apparent because that comedy was largely missing from the second season opener, and I was less satisfied by it as a result.
You can see a line here or there where the SyFy version is saying, "See, we've got comedy too!" But really, no, they're taking it a s a straight-on drama. Without the comedic aspects, the thing leans toward the derivative and turgid. The comedic aspects are what made the show different from the other urban fantasy out there.