Here is a link to the machine in question, for everyone.
The 3RT 12C is not a continuous tempering machine (neither is the 6T series), it is a batch tempering machine. From the page:
12 kg. of chocolate is melted to 45 degree C in 60-90 minutes. It is then cooled and tempered to 31 degree C in app. 20 minutes.
Once the 12kg of chocolate is used, it will take a minimum of 20 minutes to get a new batch of 12kg of tempered chocolate (assuming chocolate at 45ºC is poured into the tempering machine) otherwise you are looking at 80-90 minutes between batches working from solid chocolate. From everything I have heard, the Chocomas are dependable machines that do what they do. However, note that the these machines do not include depositors or vibrating tables so if those features are important to you you need to factor those into the total cost.
Both the Selmi One and FBM Aura are continuous tempering machines. They are roughly comparable in terms of basic capabilities. Major differences are in working bowl capacity and form factor (the One is floor-standing and the Aura is bench-top).
With the Aura's 4kg working bowl you can be ready to work in about 30 minutes from a cold start and take up to about 10kg per hour out of the working bowl without having to interrupt production for more than a few minutes at a time. This is one of the major advantages of continuous tempering - greater throughput. I would also say that more consistent crystallization is also possible.
In my opinion, based on everything I know about the internal workings of the two machines FBM machines are better engineered and built than Selmi machines. The Aura is about 2000 Euros cheaper than the One (before the ChocolateLife member discount on FBM). From a throughput perspective, the closer comparison is the FBM Prima which is slightly less expensive (after ChocolateLife member discount) than the One. The Prima does have the advantage of accepting an enrober attachment, which neither the One nor the Color can.