Pretty simple test.....anyone who tells you that a tag doesn't improve the ride, look at their profile, they don't own one. I have a Newmar, true 40' coach that has a tag. Some of the differences between it and my 37 Diplomat, no porposing with a tag, straight line stability is unequaled and the additional braking is huge. My coach with Comfort Steer and tag axle, is pretty much unmovable in high wind conditions. There have been times that we stopped for fuel in the desert and didn't know how hard the wind was blowing until we got out of the coach.
The only real con in my coach....that tag takes away 3' feet of storage bay space. My Dutch Star at 40' with a tag, still has more storage than my 37 Diplomat without. It's all about how they placed equipment. It's not much more, about half of a full size slide through bay.