I prefer to use Spiderwire Ultracast Flouro-braid combines the sinking properties of a fluorocarbon with the strength and stability of braid. An awesome product.

http://www.texasbasstackle.com/scripts/prodView.asp?idproduct=1582

Interesting comments but does anyone actually know the differences in dept when using flouro vs braid or mono? Is is 6inches, a foot or even more?

I'd go with flurocarbon

I would love to see a myth busters episode on fluoro vs. mono of the same diameter getting a crank bait deeper. If it is true that fluoro will get one deeper than I bet were talking about fractions of an inch....like maybe 1/4" or less. Between the end of your rod and the knot on your crank bait, you are pulling line through the water by force, forcing the line to cut through the water 1000's of times faster than the sink rate. The sink rate of the two lines are so minimal that it would not have any affect.

Here is a pretty good video

Interesting video

This would be cool! vs. Braid too

The sinking effect of fluoro has little effect on how deep your crankbait gets. The drag of the line size matters more. 20 to 30 pound braid will get a crank just as deep as 10 pound fluoro.

I don't believe we can react fast enough for the line stretch to matter either. I feel like that in the amount of time it takes you to react to a bite on mono vs braid a bass isn't going to be working the bait further down to his throat.

You can however rip the hooks out with braid if aren't using the correct setup and technique.

Or maybe I've just trained myself how to fish cranks on braid.