This message is old, and I am new to the forum. I have a MacBook Pro with 16GB of RAM and I also have a 27-inch iMac with 32GB of RAM (can be configured to 64GB RAM). Since I have both, I thought it would be good to provide a quick personal preference/reference for anyone who sees this post. If you edit a lot of photos and have the money to get the 27-inch iMac, purchase it and thank yourself later. The time difference with batch editing in Lightroom, Adobe Camera Raw, and doing batch automation in Photoshop is huge. Example, exporting 400 raw images from camera raw to jpg on a MacBook Pro (16GB ram) can take about 3.5 hours plus, on average 4 hours. Using the 27-inch iMac (32GB ram), around 2 hours. Another good reason to get extra RAM is because when opening an image directly from Adobe Camera Raw into Photoshop at the same time there is a noticeable speed increase. I agree with @PhilliPeake, you can never have too much RAM.

Bottom line, more is better.

More RAM is better. SSD drives are faster. Good upgrade.