2007-2014 3/4t Silverado/Sierra Questions

[72BlckButy]

I would assume there's been various changes on the 3/4t trucks over the last 8 years. I wanted to see if anyone could tell me if there's a reason to stay away from one vs. the other.

For instance, on my '08 1/2t there has been issues related to the AFM and the oil. Or the change to a 6-speed transmission and a 3:42 gear vs. a 3:73.

As a prospective buyer I wanted to see if someone on here could enlighten me a little.

Is there a pro or con for waiting for the 2014's?
Should someone look for an older 6.0 vs. a later one?
Should someone look for an older diesel vs. a later one?
Is there any issues with one year model vs. another?

Thank you in advance for any insight you can offer.