i got the digital varistream, i was told by the guy at williamson pumps that theres less chance of water getting in and theres no numpty to get broken,
one thing he did say is that the varistream replaces the switch in the pump, where other make are just voltage adjustment to control the flow which still uses the pumps switch
i used another make switch with a blue front(mentioning no names) and 2 broke after 2-3 months all with the same problem ,they took them back and fixed foc but you dont need the hastle