If i had my time back i'd go with the BDS, my next truck will have a BDS lift. they also make a 4"
I may end up with a 4" in the future with 33" tires so i can still get my truck inside the garage for the winter months. If i find some 4.10 or 4.56 gears i'll keep the 6" and just use some smaller tires, use the metric system to get 34.6" tall and 11" wide. it should tow good set up like that.
I know a few guys with diesels and 37" tires on an 8" lift and it still tows just as good as stock, with 4.11 gears.