Here's one of many pieces of information on this site about SSDs.
http://www.tomshardware.com/picturestory/689-best-of-computex.html
SSD is in a state of considerable flux and things change a lot. I have found Samsung and Crucial to be reliably good and have used 250 and 500Gb of both. BEST depends on purpose.
If you are gaming, and plan to put games on the SSD, I would get 500Gb. Modern games are getting very big (40GB+) Allowing for space for efficient TRIM, and putting the OS on as well, 250Gb will be used up quickly unless you are very disciplined. Larger drives tend to be faster than smaller drives.
What and why?