I have considered safe contractor in the past, but at the end of the day we are cleaners, not scaffolders.
As for the SCSC, we found that more and more developers were insisting on it for all sub-contractors, so all our staff took (and passed) the test.
It really depends on your activities. For example, if you are working at height and using an MEP, safe contractor accreditation might be the way to go. But if you use nothing more than a domestic vacuum cleaner, SCSC should be all you need to clean on building sites.