they will both clean well
Both machines will clean well, the difference of course is the filtration. When it comes to raw cleaning power, that is suction and airflow, the Miele will beat the Sirena hands down. The raw cleaning power of a water filtration machine, even a rainbow is about 30 years behind current bagged models. But, remember that as long as the machine has enough power to remove the dirt from what you are cleaning, it is doing its job and the water filtration machines have no problem with that. Your Miele will work just fine for your needs, but if you chose to get a Sirena, it would also work. I have a sirena and I really like it, probably going to use it this weekend actually. One thing a Sirena has that the Miele and many other vacuums do not is the ability to be used as a blower. This may or may not matter to you but it may come in handy. The Sirena can also be used to clean up wet spills, although it will not hold near as much as most wet dry vacs. I also have a Miele C1 Olympus and again it's a good machine. So it really comes down to whether you prefer a water filtration machine or a machine that uses bags.
Mike
