Bags. Bags bags bags. They can say what they want about the RAS but when you get down to it it's just another spring and is no more "active" than the springs already there. It's not going to stop the rear end from sagging, it'll just change the amount of weight it takes to do it.
I have an '08 F450 and I installed a set of bags. My truck rides at the exact same height, always. It doesn't matter if there is no weight on the rear end, or 4,000 lbs, it rides at the same height. RAS won't do that.
I installed it, I set it, and I promptly forgot about it. I don't have to worry about adding air, bleeding air, or anything else. It's just there. Shoot, when I fill my fuel tank the compressor kicks in to compensate for the weight and as I burn it up the valve dumps air to adjust.
You can't really get much more active than that.
2008 Ford F-450 "Lil Beasty"
2011 Heartland 3950 "Big Beasty"
1970 DW Made in Japan "Big Bossy"
2005 DD Made in Ohio "Big Pain"
2007 DD Made in Ohio "Lil Pain"
2004 GR Bahzu the dog "Big Sissy"
2010 Weim Mobo the dog "Fast Spaz"