In general, there are two basic user groups for MA in climbing. They each have distinct needs and equipment.
The first one, for rock/ice and glacier climbing, involves a rescue situation. Here, you typically need to haul a big load a single time for a short distance with improvised materials, the size, bulk and weight of gear are important factors, and you may likely be using a more complicated mechanical advantage system, like a 3:1 or 5:1, to raise your patient. It’s also unexpected and stressful, meaning you may have to rig a more complex haul with improvised materials, quickly, without much practice.
Big wall climbing can also involve hauling big loads. But instead of 30 feet, you’re doing it for maybe 3,000 feet! Bulk, weight, and cost of equipment are factors, but not nearly as important as in alpine climbing. You are unlikely to be doing a 3:1 or greater haul, 2:1 is typically all that’s needed even for honker haul bags. And, because you are repeating the same movement so many times, you’re willing to take some time and invest in a perfectly dialed system that uses more expensive and slightly heavier gear, if it increases your pulling efficiency even a tiny bit. To summarize:
In alpine climbing . . .
You start your climb not knowing if you will need to haul (and hoping you won’t!)
Need understanding of various MA systems, 2:1, 3:1, 5:1, etc.
Probably won’t have the exact right tools for the job, creative gear improvisation may be required
Weight and cost of gear may dictate what you choose to carry
Usually need to move a load only a short distance, so highly efficient systems are generally not so important
In big wall climbing . . .
You start the climb knowing you will have to haul
Typically only using 2:1 MA, more MA not required
Carrying the exact right tools for the job is a priority, even if they are expensive, bulky, and weigh more
You are moving a heavy load for a very long distance, so well practiced and efficient systems becomes very important