I have been using Retainer Brite to clean my retainers since getting them. During a recent trip to London, I found these new tablets so thought I would give them a try.
They look and work in a similar way to Retainer Brite, you put your retainers in some warm water (not too warm or you risk deforming them), drop a tablet in and wait 15 minutes for them to be cleaned. The only difference I found was that with Retainer Brite, the solution goes from blue to clear over the 15 minutes but with the Vitis tablets, the water remains blue.
I found my retainers to be clean and fresh when they came out and could find no difference in the performance of the two tablets. Give them a go and let me know which you prefer.