The surest way to delete all data from an ssd is to perform a "secure erase". The process uses a very small electrical charge to erase all data. It also prepares the now empty ssd for reuse. The best part is that it only takes a few seconds. Some ssd's like Samsung, Intel, and Plextor come with utilities or tool kits which include the secure erase feature. If an ssd does not come with a utility there are third party applications like Parted Magic that can do the same thing.
Hard disk drives are handled differently. When a user deletes data from a hard disk the data is not actually deleted. Instead Windows simply does not show the data on your monitor screen. The data is still there. Windows just pretends the data is erased. There are...