Strong filters cause the motor to work more, but it is slight. The big problem comes when the filter becomes clogged w/dirt.  That is when the motor really heats up.  People try to stretch their filter life or they just do not check the filter until it is too late.  This is the main reason for Bissell bagless motor burn-outs.
 
Another problem w/filters is that some brands will allow air to escape around the filter when it is clogging, instead of going through the filter.  
 
Filtration is very important.  It may not be important to everyone, but it is to those who have allergic reactions to what is being picked up by the vacuum cleaner, a/c, etc.
 
Everyone has different levels of allergies, so it is important to find out how bad your allergies are.  Personally, I do not need the most filtration, but I know that I need some.
 
When shopping for a vacuum cleaner, there is no need to find the best filtration machine if you, or the people around you, do not have any reactions. If you have some allergic reaction to what comes out of the machine, find a filtration level that works for you.  Let's not throw out HEPA all together.
 
The filtration on the Electrolux is not going to filter as well as using the final filter on it.  Later Electrolux-Aerus(USA) machines gave you a choice of putting on a final filter if you need it.  Miele gives you a choice also.

Hi guys,
 
As most consumers, I'm basicallly more concerned about the preservation of an investment.  The scenario being one involving a vacuum I'd spent some money on, I'd be far more pleased due to a filtration set-up/mechanism that not only helped clean up exhaust air but helped keep a vacuum motor clean and thus extended its life.  HEPA filters are usually expensive and that usually does cause an owner to want to be sure he/she has gotten the most use of it before having to buy a new one.
 
HEPA filters are also best used as after-filter devices in canister and clean stream upright vacs which still would mean ample pre-filtering is needed to provide a balance that pays off all around.  The problem with HEPA is that most manufacturers allow for minimum filtration area that only fulfills the hype factor.  Though not here to pitch product, I liked Nilfisk because it managed to link good airflow and high filtration potential, by way of options, into relatively compact machines like the GS 80 and now defunct 90.  These are/were mnachines that you could expect to go three to five years without purchasing new HEPA filters.  Again -- design means everything.
 
Regards,
 
Venson