Too many variables with the question as open as it is. You can see, you are getting a variable of answers, all from different perspectives.
If you don't need the extra CCC or plan on hauling a heavy load behind you, then a non tag DP will be OK to go with.
If you want the extra CCC and or plan to haul a heavier load behind you. The the Tag will pay dividends on that front.
The normal list of Pro's /Con's on the Tag vs Non Tag are:
-Tighter turning radius, due to drive wheels being set forward
-Extra CCC and heavy load towing capacity
-One more pair of brakes with one more pair of rubber patches hitting the pavement, does help on braking
-More stable ride under all conditions
-As RVNET's forum member stated 'Tags Look Sexy'
-Loss of storage bay
-One more pair of brakes, shock, tires to maintain
You can find DP tags down to 37-38' (Older Foretravel's and Country Coach come to mind.), as well as in quite a few 40' coaches too. While some 42' coaches do not have tags, most of the time when you jump to 42-45' - you end up with a tag.
One benefit of going to a 42' vs 40' DP, is you usually get three full bays, vs 2 1/2 bays on many 40' tag coaches.
And repeating the variables - not all chassis are built the same. Spartan and Freightliner are the volume chassis builders. They have entry level chassis all the way to high end chassis. Same with the engine and side vs rear radiator story to. The coach manufacturers choose/spec the price point they are looking for in a chassis, and the chassis builders provide a contented chassis to meet that price point.
Another factor on 'coach handling', is the Comfort Drive and or TRW equivalent. Many Newmar owners with Non Tag that have Comfort Drive, are very satisfied with their coaches handling on the road.
Another factor on tag vs non tag, is in some of the specialty higher end coaches chassis. Newel, Foretravel, Country Coach, Alpine, and some Tiffens, have their own specially designed chassis. Both tag and non tagged. The coaches with these chassis usually have superior handling and CCC and load towing and more rigid foundations for the coaches to be built upon.
I separated Monaco from the above, as they had the well thought of Roadmaster series of chassis. They have entry level chassis all the way up to their top end coaches and chassis. The higher up the food chain coaches, say 8 baggers and above, are well thought of as far as handling and stability.
So, OP, a simple answer is not available. But, IMO, you can make a pretty general response of 'Yes, tags handle better, and make a difference.'
Another set of opinions have been shared with you
Best to all, travel safe, have fun,