All of the continuous tempering machines at this end of the market (FBM, Selmi, Gami, etc) use the same basic technical approach to tempering. Chocolate is melted in a working bowl and the melted chocolate is transported through a chilled pipe by an auger. Crystals are developed on the inside of the pipe, scraped off the sides, and mixed into the chocolate before it leaves the spout. Chocolate that is not used is detempered and retemepered in a cycle and that's where continuous comes from – the cycle is not interrupted as it is in batch tempering approaches.
The brands differ in the engineering details and approach, manufacturing, and other aspects. It may be helpful to know that FBM introduced continuous tempering into the artisan confectionery workshop in Italy in 1977. To some extent all of the other brands copied (though not literally copy) what FBM did, with a focus on different aspects of the process.
FBM take a different approach to manufacturing – all machines are made to order, where other companies manufacture and hold finished machines in inventory. If you want a machine with a specific customization you may not be able to get it from Selmi but could get it from FBM. One example is an extended entrance section or take-off belt on the enrober.
FBM takes a different approach in engineering, building in a lot of electronic safeguards to make it harder for inexperienced operators to make simple mistakes. For example, after you turn the tempering system off on an FBM tempering machine, you cannot stop the auger until the chocolate in the pipe warms up. This is to help ensure the machine is not turned off with tempered chocolate in the pipe. This feature extends to the machine automatically reversing the auger when it's stopped to empty the tempering pipe of chocolate.
If you are enrobing 500 pieces per hour w/ 5gr/pc you don't need a tempering capacity of 75kg per hour as you're only using 2.5kg/hr. With FBM you can put a 180mm (7") enrober on a machine with a working bowl capacity of 10kg if that's what you need.
Some machines use water for heating and cooling, others use a combination of water and chilled gas or electrical resistance wire and chilled gas. There are advantages and disadvantages to both in term of cost and complexity.
Some machines are easier to wash than others but, in truth, you should not be washing continuous tempering machines on a regular basis unless there is a very specific cross-contamination issue you are dealing with. You need to take a look at the amount of time going from dirty to completely dry, not just how long it takes to remove the auger when assessing cleaning times.
In truth what happens is that one company introduces a feature and soon thereafter it shows up on other companies' machines. There's a constant ebb and flow of features and functions that makes it difficult to say, absolutely, one brand is definitely better.
I work with FBM in part because they listen to my ideas for improving machines. With my help and the help of customers, FBM built the first tempering machines specifically for high-viscosity, two-ingredient, craft chocolate back in 2013. Other companies are starting to offer similar capabilities.
So it's not a simple question. You should spend some time with each manufacturer matching your production requirements against the capabilities of specific machines to determine with is the best fit for what you want to do, and your budget. What I will say is that setting a maximum price you're willing to pay that would mean "settling" for a machine that's not a good fit is a bad idea.