I would (and did) go to Northwestern, BUT I would definitely go to both schools and visit. There is absolutely no difference in job prospects. Any prestige advantage at Michigan is countered by Northwestern's small class size. There is essentially no one who didn't have a job in his/her choice market upon graduation. This is especially true for the students who wanted firm jobs. Everyone got a firm offer. Going to California is extremely easy. All you have to do is show up during OCI, smile, and have a firm handshake. Further, I'm quite certain Northwestern placed at least as well as Michigan in clerkships - a recent change. I think there were like 16 appellate court clerks, from a class of 240 or so (I don't really know, but the number sticks out in my head). I say all this only to rebut the notion that somehow your job prospects will be better from Michigan.
Anyway, I think you need to go visit. Forget about prestige or anything else. See which campus you like better. Talk to students about the experiences they had during law school. I chose Northwestern, because the opportunities at the school were better for me. The Legal Clinic at Northwestern is unbelievable, providing students the opportunity to work with and go up against Chicago lawyers while in law school. The location in a huge metropolis also has advantages. I externed for a federal judge in law school. Many of my friends worked in various government positions which had offices in Chicago - EEOC, anti-trust division of the DOJ, U.S. Attorney's Office, etc. Finally, I wanted to live in Chicago as opposed to Ann Arbor or any other college town (sure you can argue there are things to do in AA, but let's keep things in perspective). Maybe you'll find the opportunities at Michigan more appealing, which is why it's important to visit both schools. I can only speak to Northwestern's experience.
Good luck with your decision. You have some good options, but it really does matter where you go to school depending on the experience you want out of law school.