Many things about tags...here's my take...
Tag makes the coach much more stable in winds, trucks etc.
Ride is more comfortable too.
Monaco products have 10 OUTSIDE air bags. Meaning the air bags are mounted OUTSIDE the frame rails. This gives stability to the ride comfort.
Now a caveat. Make sure the coach you get has an ADJUSTABLE tag. Mine is air adjustable. This allows me to adjust the tag pressure with a simple turn of a knob. This feature allows me to adjust the pressure/weight of the other two axles. More pressure applied to the tag, more pressure applied to the steer axle and less pressure on the drive axle. So if your weights are a little off, you can adjust for those differences.
Another feature to look for is being able to LIFT the tag. On mine, I can LIFT the tag which give me a tighter turning radius as well as not dragging the tag tires around a sharp campground turn. Max speed with the tag lifted is 5mph.
Only negatives are having to budget an extra $1200 every 7 years for two extra tires, and paying for three axles through the toll plazas.....Dennis