i read up on Brita v. PUR this afternoon, and you're right there--PUR filters a LOT more. but what about zinc? there's going to be trace minerals, etc., in any water. the next thing i did, since we already have Brita and we're bleeding $ (i always like to keep an emergency $ stash, and even more so with baby coming home).
just a thought: location may be a major factor in what is and isn't filtered. i had a long conversation with our city's water manager, and he filled me in on all the facilities and testing that goes on in our area. we are in the Chicago area, so our water goes through (among several others), a facility dedicated just to filtering and testing for giardia. our city has continual testing to back up Chicago's procedures.
my guess is that you can't count on this kind of vigilance in a more rural area, where water may not come out of Lake Michigan. research, research, research, right?