As you mentioned, yes, less weight. Stock weighs just over 25# per side and the coil over arm weighs a tad under 16# (best approximation as these are not fully welded up yet).
You are able to use the same arm to run either a coil over, or a conventional spring setup. So that is a plus.
They offer improved ball joint geometry.
They are dropped 1", so for folks wanting to go lower up front they have more attractive options to get it there versus spindles and such.
It is extremely beneficial for those wanting to shed weight. Drag racers are always looking for any way possible to shed a pound or two. Losing 20#'s up front is huge for these guys. For corner carvers, autocross, or spirited driving...you are re-distributing weight and making the truck more balanced. Same reason guys will move their batteries to the rear or remove weight from the front.
Personally, I am one of the "1%" folks. In other terms, 99% of the guys want to go fast in a straight line, the other 1% want to go left and right. My truck has Hellwig sway bars front and rear, Stifflers x-brace, d/s loop and long bars, and upper control arms. I also have a set of used Brembos I am waiting to install (if they will fit under my Centerlines).
Hope this is somewhat beneficial to you or others. Jeff