It probably wouldn't really matter whichever comes first. Normally, you work on previous weeks problems in a tutorial but there are times where the lecturer falls behind and you go over new material in tutorial's which can be just plain confusing.. (Generally more applicable for when a tute is held before a lecture.)
That said, I too agree with stonecold that most people will fall behind in tutorials, especially if they're not assessed and if there isn't a mid-sem test for that unit. Last sem, for a unit I took called MAE1042 (Intro. to aircraft structures and dynamics), there wasn't a mid-sem test, so as a typical slacker, i skipped nearly every tute and actually began working on the 1st week's tute a couple of days before the end of year exams. Did the same with MTH2010 (Multivariable Calculus) but it did have a mid-sem which I totally flunked on... however, I don't really suggest falling behind in tutorials for the entire semester as it was hellish during swotvac, where I went to Melb uni's library (closer for me) from 8 am to 12 midnight daily... Can't be luckier when I pulled off 2 80's for those subjects lol... I promised myself for my New year's resolution that I wouldn't do that again, but I probably will -.-