I have seen a fair few come and go over the years Sectron was my favourite, when I was an engineer. I think it is down to what you are used too and expect in a lot of cases. We used to use EMCS and Yeoman but found EMCS more problematic. I know others that swear by EMCS. RVR are an off shoot of Custodian I know people that swear by Custodian I always found them harder work than they needed to be, and RVR as a monitoring co the operators were rubbish, the rep was fantastic though, really knew his stuff deserved to be working for a company that used decent staff.