I HAVE USED A FANTON BEFORE AND THEY ARE GREAT VACUUM CLEANERS.
RAINBOWS BLOW DIRTY DUST INTO THE AIR AND ARE NASTY TO CLEAN UP.
YOU NEED TO GET A POWRFLITE VACUUM, THEY ARE THE BEST, AND LAST FOR YEARS.

I do know about rainbows and I have never had "mud" blow out.  I knew a Rainbow dealer and I've taken apart many Rainbows.  The reason the service record said they were so good was because it WAS 40 years ago!

I have had experience with both maintenance and selling of Rainbow
Vacuums, They do have a considerably large amount of dirt blowby. (secondary dirt)What they essentially do is throw the dirt into the cyclonic spining water. But not all dirt is captured and the reason you don't see a dust storm following you around the house is because of the humidity that is built up makes the dust/dirt particles fall back onto your furniture, walls, and floors with out any floatation. They lack a secondary filter to capture that secondary dirt/dust. Rainbow have been around for generations, so we wondered why they havn't installed a secondary filtering system, so we cobbled up one placing it in a position right before the motor exaust and that's when we discovered why. It became damp and plugged up with in 10 minutes of normal vacuuming. And pickup power droped almost totally in that time. I consider the rainbow to be one of the last vacuums I would ever recommend to a friend or family member. Now for cleaning a car they are great, the dirt stays out side the house. Just like a Kirby they are over rated and over priced. The best vaccum I have ever used is any bag vaccum that the owner has kept clean and changes the bag frequently, this goes for the bagless units as well, I would never let a vaccum go more than 2 weeks with out changing the bag. This keeps power up for better cleaning and longer moter life. What you are essentailly picking up is dead skin, hair, food partical and dirt and grim that is tracked in on your shoes, and who know where your shoes have been. Oh and the sand that the carpet manufatures sprinkle into the carpet after they make the carpet, ever waunder how they cound put a 10 year warrenty on carpet? They leave the sand off!!! It's all basically a pot luck diner for mold, mildew, bacteria, and extreemly small insects like dustmights and other nasty little critters that make us sick all the time. We once even had a lady bring in her cannister vacuum, she couldn't figure out what the bad oder was and the vacuum didn't pick up like it used too. When we removed the bag it was was churning with Fly maggots. When she returned to pic up the Vac she was asked about catching flys She was stunned that we knew about it. LOL We recommeded she start changing her bag once a week. about 6 months later she returned for a new supply of bags, she couldn't stop talking about how her daughter who had sever cronic breathing problem,  
(asthma or alergy's) sorry I don't remember which, but she couldn't stop talking about how her daughters problem and decresed to a point where just about the only times she had problem were when she was staying at someone elses house.
By changing the bag often you not only are keeping your bag which is the basic filter (Cleen) but you are also not alowing the the stuff inside to begin to rot away.  
Now the greatest thing I have discovered is what is called an Alpine Air Ozone machine. The ozone machine runs constantly in my house, What this ozone does is reconfigure the moleculer  structure of airborn particles, making them heavier and keeps them from floating around, I need to dust more often now, but the air quality is much better, just looking twards the sunlite coming through a window, i no longer see the dust flying around, Sometimes I'll shake a curtain and watch the dust get stired up into the air, then watch in amazement as is quickly drifts to the floor.  
I would challange anyone who wants to religiously defend a Rainbow to take any bag Vac and their rainbow and insert a new bag and fresh water, then go ahead and Vacuum  their house with their Rainbow, then turn around then re-vacuum their house with the bag vacuum. Then take their rainbow water and put it into shallow pans out side or even in the oven and let the water dry up, then take whats left and  weight it then take the vac bag and weight it, subtracting the weight of an empty bag, and what you will find is ???????   DO YOU REALLY WANT TO KNOW????
 
ok ok the bags contents will be approximatly 2 times heavier. AND IT will have a considerably larger amount sand (heavier particals) in it too.  and this is after you have already Vacuumed with the Rainbow water Vacuum.  
No mater what your decision is on a Vacuum the most important thing to keep in mind is change your bags and or filters atleast 2 times a month or more based on your needs. I never buy bags at a retail store, I buy them at Vacuum repair shops in large quantity, When I am low I take 15 minutes and call around to all the places that carry my bags and ask what their prices are and the numeber of bags at that price, I have discovered that after the second call I now have 2 prices and when the 3rd call if it's not an even better price I always ask if they can do any better because another place you called gave you a beter price and I always let them know I am going to buy about 20 - 40 bags at one time. they almost always will lower their price to be alittle lower than the one before, but not always, but by the time I have called 7 different places i have finially lowered the price to about a third of what you will pay at walmart, or the local grocery store.  
 
Now about the bagless vacs you still have to deal with replacing the filter or it will plug up and reduce the power to pick up dirt. They are very expensive, and you can't just take them out and shake them out. They will need to replaced 2 - 3 times a year to maintain that New vacuum rated pickup power. When averaged side by side with bags the price of a filter over a year compared to bags is more expensive.   so educate your self before you make your decision.   Best wishes  Larry