I have had both.
The Roadmaster was on a half ton truck and was used for towing a trailer. It was an absolutely excellent choice and when I had not trailer attached the Roadmaster still improved handling. As you know, the more pressure on the Roadmaster the more it works, less pressure, less work. Easy to install too.
I use the Big Wig on my Ram 3500. The BigWig is not bad off road to be honest. I have taken it through some fairly gnarly stuff in Utah with a loaded truck and camper. Strangely, the main issue I have with it is when going over bumps like a speed bump off centre, the swaybar holds the truck in place so it rocks quite a lot. I never notice that issue off road however.
The Roadmaster does what it says on the tin. Handling improved loaded and unloaded. It did reduce some roll but will not reduce as much roll as the Hellwig. The Hellwig will not make much difference to the straight-up ride like the Roadmaster does though.
The Roadmaster is effectively extra leaf springs. Less when you don’t need it, more when you do. I am full time in my camper and do a fair bit of off-road so I went to Deaver Springs and had my leaf packs rebuilt to suit the full-time camper weight.
I am considering removing my rear swaybar to see what happens. (I had removed my front once for mechanical issues and that was awful!). If I don’t notice too much extra sway I may just leave it off for a better ride on the bumpy stuff.
Not sure if that helps you.
2007 Dodge 3500
[5.9 Cummins, Stick Shift] + [XPCamper V1E]