Hi tarnold,
You ask a good question.
Installed by a shop, we have front and rear Roadmaster bars on our 2007 E350 chassis, and I am very happy with them. I since have helped my brother install a rear Helwig bar on his 1998 E350 chassis. We installed it together and we did NOT have to drill anything. He is happy with his. He has more miles on his than we do with ours.
So there you have my answer....both are great. But knowing what I know today, I would install Helwigs on our rig myself and save the money.
One more point. I did not see any notable difference in the quality of the parts either. The Roadmaster was more colorful, meaningless to me. I actually prefer Helwig's front bar mount better for our particular chassis.