The reason im asking is my gpu died a while ago, so im upgrading it, and i decided to etheir buy an SSD or another hard drive. I run a hackintosh (os lion) and windows 7 so i figured the 1tb hd could give me more room when im on OS lion. But tbh i barely use any space lol, but its good to have.
And i rarely cut off my computer etheir, i may cut it off like once every 2 weeks, but besides that i dont really cut it off. So i wouldnt really see the benifit of a SSD since most people say it speeds up their start up time. I dont do much ( or any ) video editing/photoshop stuff etheir. I only really play world of warcraft and league of legends lol. and browse the internet.
The main difference is caused from the denser platters but it probably won't be a noticeable difference between your 640gb hdd. The main benefit of a ssd is access times which speeds up loading of any file/program. Ssds are just starting to get somewhat affordable so the decision to get one is really up to you. It would have been better if you just kept an eye out on good deals, 60gb ssds usually go on sale for $60 like one did a couple days back.
Based on how little difference I've seen between a seagate 7200.12 and the WD 1.5TB you won't see a difference between spinpoint and WD or between any other two fast 7200 rpm drives. You will see/feel the difference between a fast 7200 rpm drive and a slow/green drive.
The speed of the head movement is tied to power consumption so green = slow. Faster head movement yields better random access. Denser platters = more bits move under head per revolution = faster sequential access. Faster RPM means less time waiting for the right data to spin under head and more bits per second going under head so better random and better sequential.