I've had a Mexican and a Squier VM Modified amber bass (maple body). The MIM sounded OK but fell apart: pots stopped working, screws came out, the neck couldn't be straightened anymore, etc. Maybe it was bad luck.
The Squier also sounded OK, was much sturdier, and felt much better to play than the MIM. I compare them to the MIA, and here's what I think: If the Squier is made from other body woods than the MIA, it will not sound the same. Sure, John Myung plays a basswood bass, but it's not a Fender type bass. Fender type basses should have alder or ash bodies in order to have the Fender sound. I compared the Squier with a MIA, and even installed the exact same pick-up on both (Seymour Duncan SPB-1) and tonally it's much, much poorer and has much lower sustain. The MIMs may not be as well crafted, but at least the wood is right. So if you buy a Squier and change the pick-up, you still may not get the Fender sound, while with a MIM you could achieve that.