We've got the TrailAir TriGlide and like it very much. It has to be greased on a regular basis but that's not a big problem. You do need to have the air shock pumped appropriately.
We did get ours when Lippert was running a special so it's not quite as bad a sticker shock as it could have been.
The Demco without the airbag and not needing greasing could be an advantage. My advice is to look at both.
Al & Linda
2013 GMC Denali 3500HD SRW, Crew Cab, Std bed, 6.6L Duramax, Allisons, PullRite Superglide, Triglide
2011 Crossroads Seville VF35CK11