The was an old saying: "every pound on your feet is an extra five pounds on your back".
I've used low-top hiking boots (Merrills are mine) for back-packing, ankle-high Gore-Tex, and heavy leather boots. It's all a trade-off: weight vs. support.
Another factor is wet-weather protection. Ankle-high boots provide better rain protection, but using gaiters is advisable regardless of what kind of boot is worn. I forgot my gaiters this week and ended up with soggy feet...LOL.
