Keeler Krap...
The keeler bagless thing is just a bunch of Eureka/Electrolux parts designed for negative-pressure vacuums glued onto Kirby hose-ends, it is highly inefficient and relies on those cheap and nasty cartridge filters that love to clog up, especially when air is forced through them under positive pressure, it isn't going to work as well as a proper bag setup (Shakeout or disposable) as the Kirby is made for a large surface area for filtration, not a tiny little filter...
As to the "What is cloth?" question, well, that's already been answered, Cloth is a sheet of woven fibres, either natural or man-made, Felt is just that, felt, it's pressed wool fibres made into a felt sheet with heat and pressure, you could say the polypropylene bags are a form of Felt, just made from a man-made plastic instead of animal fur...
Just so you know I live in a part of the UK where the cotton industry boomed, so I grew up learning a lot in school about making cotton thread, cloth weaving, felting, clothing manufacture, etc., so I'm pretty sure I know the difference between Felt and Cloth, and a Polypropylene bag is not a Cloth material, it is pretty much a felted, heat-bonded fibrous material, and is not made on a loom which would make it a cloth...
And yes, filtration matters if you suffer from allergies, you never know what is in the carpet that has been dragged in on your feet, or blown in through the doors, windows or ventilation, if your vac is picking up allergens and spitting them back out, then, I wouldn't consider that a decent vacuum cleaner, thankfully I don't suffer from allergies like some do (I do get minor irritation when working on dusty and dirty things or using my Kirbys with their shake-out bags), but the mother does, and I do have to be careful with how I look after my vacuums and what they put out from the bags...
Not to mention, I'd much prefer a bag that doesn't compromise the airflow of my vacs, less surface area for filtration means less airflow means less pickup, and less pickup means there's no point in vacuuming if you're leaving the dirt in the floor...