Memory is memory, apple just sells other companies stuff anyway so they dont really have their own memory product. A good place to buy is from
www.newegg.com great prices.
All memory is by no means created equal. There can be very significant performance differences both in how memory is spec'd and different brands with the same specs. Even different product lines within the same brand will vary greatly.
If you are concerned about performance, it is generally a good idea not to go with any of the value series of RAM.
This is not the thread to get into a discussion about aftermarket RAM, but now that you know there are differences, there are tons of threads out there about it.
All of that being said, Apple RAM is way overpriced. Unless your time is more important than money, never buy Apple RAM. Take the time to do some research and find high quality RAM that is known to pair nicely with the MBP. (It's been a while since I've done the research, so I don't want to post potentially outdated info.)
I will give a couple general tips though: Even though it is usually not required, better performance is often seen in the real world when the memory is matched (same brand, product line, etc.) A good place to start is to take the memory cover off your MBP and look at what is already in there. If you buy the "same" (different size though) RAM that is in there it may not be the highest performing option available but your reasonably assured it will perform well.
