What does Nikon D7000's 2016-pixel RGB metering mean in practice?

Would you say it is a factor you should consider it over the D90?

No. While I'm curious to see what it is like the D90's matrix metering was already quite accurate.

I would consider the D7000 over the D90 for it's sensor and Ai meter coupling.

If you know how the meter works, then any metering is good enough. This is especially true in digital where you can see the results immediately and computer can help you adjust a little of exposure too.

People who used spot metering used to learn about the spot size and 18% grey cards. So did the people with center weighted metering! Correction was needed for anything that deviated from the center grey like white snow or dark clothes.
With evaluative metering now it pays to learn about filter factors and how the meter underexposes photos made with dark filters on the lens.

To answer your question - metering among these two models will not be a factor if I plan to buy one among these.