I like Rattle's Part II better than his Part I. His Part I sounds a bit frantic in places - especially at the end of the "Gloria". Also, the "redbook" issue of Rattle's M8 doesn't sound all that great. However, that's much less a problem in Part II, than it is in Part I. Both Bertini and Rattle have glorious sounding orchestral postludes at the end of Part II. On the whole, I do like the Bertini better. But here's one thing you might want to consider:
. . . burn Nagano for Part I - assuming that you own a copy - and Rattle for Part II. I find that they're complete polar opposites; and as such, have opposite strengths. For me, Rattle's big sounding childrens choir is the cement that holds much of Part II together. On the Nagano, the childrens choir is rather anemic sounding. Rattle clearly has the better tenor soloist as well (I really dislike Nagano's tenor). Nagano/Rattle - remember that. Hey, it's just a suggestion!
Barry