I am just geussing but I think perhaps the center of the tower would be the most likely to buckle. Perhaps it also denpends on the type of tower.
My thought is the flexing force if it started swaying perhaps in a gusty storm would be greatest at the center. The top is kinda free to float around without much stress from bending till it hits something solid that does not move. The closer you get to the ground or wider area is where you get to the part that does not move much. Now looking at it from the ground up, the legs or base can't sway and move because they are solidly planted, so the bending flexing force would be greater the further you get from the solid base. I would think the two points would meet near the center myself.
Of course like any chain, it's the weakest link that breaks, so if you have a bad top or bottom that would go before a strong center.
Looking at real life, most things that get blown down seem to be about center that they break also. Pics of towers standing fine half way up, the rest on the ground. Trees in a bad storm, unless the roots don't hold or they are rotten normally they break in the center.
We had a toronado come through nearby a few weeks ago. It trashed a ton of good healthy oak trees. Most broke in half in the center. Some up rooted. I don't think I really saw any that actually "broke" at the base though. Not sure if any healthy trees broke the trunks at the tops or not, I don't think so, I saw some that were hollowed out (rotten centers) that broke at the top. Many solid healthy trees snapped off about center.
It was a mess all over the road and crews cleaning it up as I drove by.