Here's Apples TN on what you'll need to do to replace your current memory How to remove & install memory Make sure you use good ESD practices as you can damage both your system and memory if your not careful.
You'll need to use PC3-10600 DDR3 1333 MHz. Using anything higher doesn't improve your system.
As to who's to use on the most part there is little difference between them. Yes, some claim to be faster under testing. The truth here is your system will rarely benefit from the difference. Look at price and what will fit your system (some have height issues).