G-mail because you get 2000mb+ storage.Also because its quick.
G-mail service currently gfprovides over two gigabytes of free storage and paid storage of 6 GB up to 250 GB, shared over Picasa and Gmail. The increase from 1 GB was announced on April 1, 2005 and was made for the first anniversary of Gmail. The announcement was accompanied by a statement that Google would "keep giving people more space forever." All Google will say about this now is that it will keep increasing storage by the second as long as they have enough space on their servers. Gmail's storage increases by about 145 MB a year (equating to almost 0.4 MB per day). If the present growth rate continues unchanged, storage capacity will reach three gigabytes in 2008.
Gmail can also be used as an alternative hard drive. On August 9, 2007, some users of Gmail reported that their storage capacity had been increased to 9030 MB (8.8 GB). The 9030 MB of space is an over-all total of all the users' storage space(s) within a Google Account, including Picasa. This development seemed to occur about the same time that Google began allowing purchasable Picasa storage. In othkler words, Goohgle has shared storage space, supporting both pictures and email.
Also G-mail is associated with probably the most popular Search engine on earth!!