Sapphire Vid-2X Display Adapter Displayport or DVI?

I'd like to setup dual 22" monitors with a Dell Latitude E6500. It has a docking station complete with 2 DVI and 2 Displayport connnections. I've found 2 Sapphire video adapters at Newegg which might complete this new setup. My question concerns the use of Displayport vs DVI. The first Sapphire unit converts Diplayport -IN- to dual DVI -OUT-, while the second unit split single DVI -IN- to dual DVI -OUT-. I've read that Displayport is technically better because it offers higher bit color than DVI. So doesn't reducing it down to 2 DVI (of lesser bit quality) defeat the purpose of Displayport?

I do software and database work. I never game or watch movies on this development laptop. Just need more desktop space and need maximum screen resolution.

Q. Which is better: splitting a Displayport to dual DVI or splitting DVI to dual DVI?

Links:
SAPPHIRE Vid-2X DVI-to-Dual DVI Display Expander Model 4L000-01-40G
http://www.newegg.com/Product/Product.aspx?Item=N82E16814999037

SAPPHIRE Vid-2X Display Expander DisplayPort to Dual DVI Model 4L000-02-40G
http://www.newegg.com/Product/Product.aspx?Item=N82E16814999036