Most stable/fastest OS X version for an old MacBook Pro I have a MacBook Pro (15-inch, 2.4/2.2 GHz, mid/late 2007) that has had a few graphics card problems. The logic board has needed replacement a couple times, meaning we stopped using graphics-intensive apps, and it has just gotten slower, and the hard drive is becoming full (obviously that will need to be dealt with).

Are Mavericks's performance improvements (App Nap, etc.) enough to make it not slower than 10.6.8? Stability is key, and I'm not sure the graphics card can handle it.

With goto fail and the other bugs that have yet to be discovered, I'm not sure when it would be a good idea to upgrade.
My brother owns a Mid-2008 MacBook Pro and installed a fresh Mavericks. In his opinion, it is worth doing this since Mavericks' performances are better than the Lion and ML releases.

However, he did replace his HDD with a SSD drive to make its MBP fast enough to run Mavericks.

So I cannot encourage you to install Mavericks on your older MBP without changing some components (and at least remove some stuffs from your hard-drive to get more space).

About the Mavericks bugs: the two updates made the things better, even if there are still some annoying issues. But that should not be your choice criterion.

My advice


Make a Time Machine backup of your MBP and give a try to Mavericks (with a fresh install).
If it is too slow on your MBP , you will have to re-install a fresh OS X 10.6, but this will probably be a good thing: having a fresh install sometimes solves some annoying issues.
if it is OK for you then let us know your experience