Hey,
I just wanted to chime in w/ my input and let you know that your chances of a full-ride at WashU or Mich may not be as slim as you think (i.e. I would suggest that you don't view your chances as being so nil to none that you stop considering both of the schools as valid options just because of that reason).
I haven't been following the pre-allo threads recently so I don't know if initial merit offers have been made yet. HOWEVER, the merit scholarship offers can keep coming and the keep changing (i.e. increase) up until late in the app season (I think up until May 15, or whenever the final decision date is). Pretty much, merit $ will be offered, and the when some students turn down that money (usually after waitlist movement occurs / more financial aid award info becomes available), the funds will be offered to other students.
the rest of what i have to say is anecdotal and doesn't really imply anything specific about your case other than don't discount your chances of getting a full ride to Mich or WashU quite yet, so take it as you will...
I was accepted to both Mich (OOS) and WashU last year. Applied for the Olin / general merit funds at WashU, didn't get anything. Mich doesn't make you apply separately for merit funding, and I got $15k awarded the first day they were sending out merit $ notices. This was despite interviewing on the last interview day and nabbing one of the last few non-waitlist spots in the class. I got a full-tuition scholarship elsewhere and I tried seeing if Mich would match or at least increase the merit $ amount, just to see what would happen and to make finances play a negligible role in my decision-making. Mich didn't budge / didn't change the amount. Since I liked the school that I got the full-ride to for multiple non-monetary reasons (in addition to the nice funding), I ended up going there.
As for Mich, I know in the past they've been open to negotiating for increasing merit aid. Three of people I know (older classes, not last year's app cycle) were Mich in-state, admitted on 10/15, got partial but not full tuition initially. Each got into other schools (Hopkins / Yale / Penn) and used those admission offers as leverage and got full-rides to Mich. Two of them got into those other schools off of the waitlist in May. I have heard of a couple other cases (in-staters though) who used either offers (admission or merit $) from better-ranked schools or better merit $ offers from slightly lower-ranked schools to get Mich to increase what merit $ they would offer. This may vary greatly from applicant to applicant though. I think it all depends on how much they want you as a member of the incoming class. They have their whole point system for figuring out admission offers and then merit $ initial offers...I think that's probably also playing a role in whether they'll negotiate or not with you. I don't know if they have a preference for negotiating w/ in-staters (esp since full-tuition awards for in-state would be less $ than full-tuition awards for out of state people). However, since you were admitted on 10/15 (i did some MDapps glancing), it shows that they at least wanted you enough to admit you on the first possible day, and thus may give you merit $.
Another example which runs a little opposite from the previous examples...
I know a Mich in-state person who got admitted into both Mich and WashU. No initial merit $ from either, but was an alternate for the merit scholarship at WashU. Tried asking for $ from both early on (just using admission offers as a basis), but no luck. Ended up getting full-tuition to WashU in May, a few days before final decisions had to be made.
Pretty much, it's not over til it's over. Waitlist movement will occur. Merit $ offers can change (and get better) up until the last minute, especially with waitlist movement as ppl w/ full-rides somewhere give them up after they get off their top choice's waitlist.
I'd recommend going to either WashU or Mich's 2nd look weekends. Pick whichever one you liked better from interviewing and go. Both had a lot of school/area-specific activities planned for the weekends and gave out nice free stuff (i.e. bags or sweatshirts) w/ the schools' logos + had & lots of free food. It was good opportunity to go and see who your potential future classmates would be too. There were a bunch of people at both who were deciding b/t other schools, but there were many at both who were definite members of the incoming class and wanted to go to get a head start on the housing search + meet people. The 2nd look weekends were great for getting to hear about the perks about the schools and the locations, for meeting people, and getting wined and dined.
You could go, and end up being able to see yourself being happy at either place, and if the merit $ thing works out, have a good thing going on. Or, you could go, and realize that you could never be happy as a California transplant in the Midwest. Then, your decision will be even easier as you could cross WashU and/or Mich off your lists and not look back and wonder, what-if.
good luck! hope this helps & wasn't too convoluted to follow.