I'd like to mention two (quite different) factors: the time it takes the journal to accept the paper is a serious consideration: however outstanding your papers, it's probably useful for it to be accepted in famous journal X instead of submitted to famous journal X when you go on the job market. I think the AMS periodically publishes average processing time for journals in the Notices.
Another factor I've come to try and consider is how expensive the journal is: journals like Inventiones are extortionately expensive compared with AMS journals (including JAMS, to give a journal of comparable prestige). Rob Kirby has information about this on his webpage, and probably there are more recent sources too. Of course I think this criterion is easier to use when you're more established than when you're starting out.