I own 2 MIJ Strats from the E series(1984-87), and if you can find one, get it. Very nice guitars. I also own 3 MIM Strats(1996, 2001, 2003) , again all very nice, different, but nice.
Each individual guitar has to be judged on it's own merits. I have played some MIM Strats that I did not care for, so they can vary. MIJ guitars seem to have the nod in quality tho.

I have had half a dozen MIM strats and loved them all. But, i just picked up a crafted in Japan 50's strat and the difference is night and day. The 50's strat looks and plays alot better than the MIM. The Japan strats are alittle more money, but worth it.

The fender guitars that came out of japan in the 80s where better than the american fenders. Thats why fender put a stop to having them imported .They where doing most of the reissues at the time i have three japanese teles from that time including a 72 thinline with just phenomanil craftsmanship and my baby a 1985 62 reissue with a rosewood neck that just keeps getting better with age.All my strats are american though a Beck,Clapton and an ultra which are just as solid an instrament can be.As far as the made in mexico ones go there where a lot of complaints when they first sarted making them but ive been told they are good now.If you have a choice in my opinion its a no brainer but try to get the ones that say made in japan over crafted

I would go with the MIJ only because I already have a MIM