I think this needs to be more of concious choice , of which system meets the requirements of the job in hand. Bearing in mind that in reality you can only skim over SC after 5 days of curing and drying. If I have a small single storey extension with say circa 30m2 F+S to blocks in it. I am mindful of the fact that the builder will want continuity on his project and will be none to happy if I piss of for 4 days while the float coat is drying. In this instance I am going to choose the Gypsum light weight system over SC as the job will be over in a day.That said, I chose SC on a huge barn convrsion with over 500m2 in it. I sprayed the lot with CPI , and then turned round to set it.At the end of the day, these sytems are there for us to choose as we feel fit for the project they are used on.
The trick to setting on a bit of suction is to lay in extremely tidely, then when 3 trowels width in make a quick flattening pass to the first bit. Essentially you are doing your first trowel alongside laying in. If you dont get the finish real good on your first trowel, then your going to struggle full stop.