Does 5D mk 2 under expose?

I have owned, and still do, the 300D and 450D camera. I found both of these models frequently over exposed resulting in clipped highlights. With my somewhat new 5D mk2, the opposite seems to be true, it under exposes. Where as with my first two cameras, I seem to frequently set the EC to -2/3 under. With my 5D 2, I seem frequently have to set it to + 2/3rd's over.

What is your experience?

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An excellent lens lasts a lifetime, an excellent DSLR, not so long.