Oh they will both bend easily if you fall into them. The rectangler one will take a little more of a blow.
The rectangler one can do more damage to your body if you fall into it for sure.
If you get the tube be prepared to treat it as a disposable item. I saw many bend this summer.
A bunch of guys in our fleet are now sailing with cut down sunfish upper booms which are the same extrusion but half the price as the boom nacra sells.