There are a number of Fresenius models. In Australia, the more recent 5008 series include the 5008/5008S systems that offer online HDF, and the New Generation 4008S NG that allows both bicarbonate or acetate dialysis, single-needle click-clack, as well as isolated ultrafiltration and sodium profiling.
In the US, there are also the 2008T, K2 and K@Home (the Baby K).
The main difference is the ability of the 5008 series in Europe and Australia to add the HDF option.
In the end, all are good, reliable machines.