MDS - Lackey for now.
Burnett was good for a good chunk of 2009. His ERA was better than his peripherals but his ERA+ better than league average. That was the first year in New Yankee, so it is not a nothing to have a righty put up that kind of performance. He pitched 200+ innings for a world series winner. At least they got something out of him.
Lackey had a winning record, but that is about the only positive you can say about his 2010. He pitched 30 fewer innings than Burnett did in 2009, with more than a half a run worse ERA. Also, because the Red Sox have less resources than the NYY (it just is a smaller market and the value of the franchise is much lower) and are less willing to go deep over the luxury tax threshold, the impact of the misspending impacted the team's decisions more than the Burnett deal did for the NYY.
Werth will be a bad signing in terms of value, but until you show me how it impedes the team's progress, then it is better than the Lackey signing. It has the potential to be a bigger negative if the team has to let Strasburg, Zimmermann, or Harper walk, and shys away from key signings because of it, but right now, it is no more of a lead weight than the JD Drew signing was.