Searched a bit but couldn't find the answer I need. So I have an iMac 21.5-inch 2010 with 2 x 2 GB 1333 MHz RAM and 2 empty slots. Now I have 2 x 2 GB 1066 MHz RAM spare from my upgraded MBP. Is it worthy to put the 1066 RAM on the iMac? I guess it's a trade-off between speed and capacity: 4 GB, 1333 OR 8 GB, 1066, am I right? Any suggestion? Thanks!