If it says 7200 RPM then it's not a true solid state drive since that is a reference to the spindle speed of the HDD platters. It might be one of the hybrid drives which has a small SSD chunk it uses for faster caching of commonly accessed data I just looked it up, I'm guessing you are looking at a seagate momentus XT as that 500GB drive? It has 4 GB of SSD and 500GB of HDD, where as that other one is a full 256 GB of solid state goodness.
But look at the other SSD topic, unless you have the cash to burn, most people go with 60-120GB SSD for windows and a few programs for the extra speed and performance, then a regular HDD for storage.