Stimulus: tax cuts or government spending?

These posts from Mark Thoma and the articles they link to are probably the best easily-read summary of the current debate from the Keynesians (Krugman, DeLong, Thoma, and others), and the self-hating Republican Keynesians (Greg Mankiw). I don't see myself as ignorant on the subject, but I also don't pretend to know enough to make any kind of really good judgement call. Nevertheless, I tend toward the government spending side of the debate (oh, like you've never agreed with something you didn't 100% understand because of your personal ideological tendencies).

I do understand Mankiw's point that spending should meet a cost/benefit analysis. Our national infrustructure could use some work . . . smart electric grid and bullet train system anyone? How about health care reform?