Panazza,
I have to agree with most of the posts in this thread regarding the quality and sound/tone of the MIAs versus MIMs.
I also have first hand experience in buying an "expensive" Fender which fell victim to Corona's poor quality control. A search of the Basses forum will find my old posts about buying a FMT 5 string (that's the one with the highly figured body top, lists at $2,400)and finding out that the neck was totally crap - right out of the box. The neck was extremely bowed and stayed bowed, even after I maxed-out the truss rod. Fortunately, the dealer gave me a full refund. Needless to say, I have no confidence in Fender USA's quality control. On the flipside, yes, I've played a number of MIAs that were wonderful basses. I just got a lemon.
Finally, I'd also like to share how I walked into a local music store and tried the four MIM P basses that were hanging on the wall; and low and behold! I found one that played perfectly. In minutes, I got the action and neck relief tweaked just how I like it. IMHO, the workmanship and finish on this bass is equal to, or better, than most Fenders MIAs that I've seen. The pickups sound decent, but I'm still going to install a set of SD Hot pickups. I'm extremely happy with this bass.
In my estimation, you're doing the right thing by starting this thread as your personal research on this matter. My only suggestion is to try as many basses as you can. You might luck out just as I did, and find a really great MIM!