JK,

Drift fishing is fishing where the rocks are. Two MAJOR points to consider:
1. Mono is more abrasion resistant than braid. period.
2. Mono is easier to tie a quick, strong secure knot with. period.
Nuff said.

However, it is possible to have the advantages of the braid (sensitivity, strength, castability, etc) as a main line and still retain the benefits of mono on the "business" end of your line as has been described earlier in this thread. That is if you don't mind an extra knot in your line. Remember you only need enough tippet to minimize abrasion to the main line. And double uni knots slide through the guides just fine.
By the way, this visibility thing is way down the list of line priorities in my opinion. Over the years I have proven this time and time again. In trying to outsmart fish I often found that it was I that was getting hornswaggled. Today I am concerned about line visibility only after I am confident about every other aspect of line performance for any given situation.
I say, put confidence before deception.