Cmon Pip put it into your own words surely you got taught that at school
What it doesn't say even though it is the same max throughput, ATDMA due to its time sloted upstream channels can cause packet loss when sending data packets to a destination, etc.
Again SCDMA is superior, in the fact as said it can handle 128QAM and use TCM. And Asynchronous upstream channels, even to us it is unnoticeable for the ATDMA timeslots but to the modem etc it is eternity :P