I have the MAF 3" drop brackets. Have been running them for nearly 5 years. Search my threads, my truck isn't a mall crawler in any sense of the word. The one thing that people conviently forget with caster plates is they make the front of the arm hang down lower from the axle. So, if you're looking at which creates the lowest point on the vehicle, caster plates do! Lots of people reject the drop brackets based on the kit that drops the front and the back. That definately creates some lower hang up points, and I wouldn't consider that myself. The front though, no big deal. I've never had them prevent forward motion, and only once did I have them catch backing up in a rock garden - and that was such an extreme case I would have had issues reguardless of castor correction method.
There is alot of BS about the drop brackets out there, but the one thing almost no one will disagree with (there is always one idiot) is that the drop brackets maintain the factory motion of the axle better and give better road manners. Not that caster plates or arms or bushing give bad manners, but the drops give better manners. At 5" of lift and 37's I spun my truck 180 degrees on dry pavement at 50 ish in an emergency situation, and the truck handled as it should and didn't roll (do a search for "how to empty your bowels"). Spike jokes about people with them wanting to sell them, and I think that has more to do with people wanting to be one of the cool kids, not one of those dorky kids with the drop brackets than it does with any real performance issues.
The question that should be asked though is why do you think you need 6" of lift? 6" of lift pretty much necessitates a DC DS - reguardless of caster correction method. If you use L-shocks you have lots of compression travel and almost no extension. There is just alot of cost associated with it. If you're goal is to run 37's, there are lots of guys doing it on alot less lift. Or, you can go with a 4" suspesnsion and a 1" body lift and have much fewer issues and you can do both of those combined for less than a 6" lift will cost you. The 1" body lift also helps w/ doing a high clearance exhaust system.
A legitimate alternative to arms to accomodate 6" of lift is flipping the radius arms to the top of the axle. It's just a matter of cutting off the mounting brackets on the axle, and rewelding them in the appropriate possition (caster wise) on top of the axle. Much cheaper than arms or drop brackets. It also gives the most clearance of any option - road manners should be very close to a caster plate set up since the motion of the axle will be almost identical (motion is determined by the distance from the radius arm mount on the fram to the center of the axle, it doesn't matter if arms are on top or bottom). This is a popular option down under. The trend here in the states seems to be either lower lift, expensive arms, or a custom radius arm or 3-link set up.