i'm a fan of both the datograph and the double split and have worn both.
if you're comfortable wearing oversized sports watches (think AP ROO or roger dubuis easy divers or panerai), then you shouldn't have a problem with the size of a DS. (the increased weight may prove to be more of a consideration, however.)
i love the datograph and wore it on a daily basis for quite some time... but i personally find the diameter of 39mm to be a bit small, esp. in proportion to the height.
the cost difference between the datograph and the DS does seem quite significant, however... granted, the datograph price in my head is circa 2003 while the DS price in my head is circa 2006, so perhaps the gradual price increases in between have 'evened' things out a bit.