Right now I have a 128GB Kingston SSD in my 17 inch Macbook pro and it's plenty fast. The system reboots in less than 30 seconds and most applications rarely go past 2 bounces before opening. The issue I am having is that I want to add more files to the SSD and i'm afraid the space might limit me. It has been a week since I've last restarted my computer and all of the apps I use are already loaded into ram (8gb). If I continue to use my laptop like this, would I notice any speed difference if I replace the SSD with a hard drive? I know SSDs speed up boot time and app load time so does that mean that if I rarely reboot and already have all my apps loaded, the performance of a ssd and hdd will be the same? Btw, the hard drive I'm thinking about getting is either the 500gb momentus XT or the 750gb scorpio black.