In theory a one-piece tube is stronger. In the real world I guess it depends on how much abuse you give the scope. I honestly can't say from real world experience that you need a one-piece tubed scope.
The most abuse a scope of mine ever had was with a Nikon Pre-Monarch (which today is essentially a Buckmaster). While I was hunting, my rifle slipped from my hands and slid down a step hill many feet until it eventually stopped on the side of a big bush. While going down I'm sure it hit some rocks and other structure. I thought that the scope was broken for sure. Well, believe it or not, there wasn't even a nick on the scope, and the optics were fine because I had scope covers to protect them. I think that there were some very minor and light scratches, but nothing serious. Still, rather than taking a chance on an animal, I just took it to a side of the hunting property where I checked the accuracy. Guess what? The bullets were still bull's eye!
Now...would a two-piece scope hold up just as well? I honestly can't say. What I can say is that I was very impressed with that scope (which happened to be a one-piece tubed scope), so I personally just buy scopes that are one piece.
I've used the Legend and they are great scopes. Optics seem a tad bit better than even the Elite 3200, but I can't say (from real world hunting experience) that the Elite 3200 is a stronger scope than the Legend.
Zachary