A few things:
-- Most canisters have a cord winder, they only fit a certain amount of cord. Most are 25'. The longest by far is the Sebo D4 and in my mind that is the only benefit of that machine. The Tacony Riccar & Simplicity lines are 28' most Kenmores and Panasonic are 24'- 26'
-- Most canisters on the market are made out of special well tested material that is known as "crush proof". You can step on it, crinkle it up, and it pops right back to life and some how electric current still works. It seems cheap and has a tendency while vacuuming to cut off suction when hose gets full tangled and twisted. But when you straighten the hose out everything pops back to life again. There are only a few companines without this style that still use the thick rubber, and primarily they are Aerus and Panasonic. Panasonic also makes the Kenmore canisters.
-- Most canister hoses are 6'. The Hoover, basic Kenmores, Mieles are all about 6'. Riccar/ Simplicity, Sebo are about 7'- 8' long.
-- Are you an allergy sufferer, I am. However despite being an allergy sufferer I do fine with the filtration on older Hoovers, new Hoovers, Kenmore's, Panasonics. If you are severely allergy allergic or are fearful of dust then you'll the newer sealed systems and excellent S Class HEPA filtration from Riccar, Simplicity, Aerus, Lindhaus, Miracle Mate, Sebo and of course your Miele.
-- As many of stated, there is no perfect machine. Just like there are Vanilla, Chocolate and Strawberry combo pack flavors of ice cream with everyone having a favorite there are many vacuums out there. The one to get depends a lot on the surfaces in your home. If you have hard wood floors, you want rubber coated or non marring wheels this would be the Royal Lexon SR30020, Simplicity, Miele and many others.
-- You mentioned your Miele power nozzle struggling on your thick carpets. Are we talking about 1" long very dense high pile carpet, 2.5" loose weave yarn style carpet or a shorter style yarn/ wool that's a little fluffier and dense but not as dense as a standard medium pile. For any of the looser weave carpets a manual height adjusted power nozzle is probably your best bet, such as Riccar, or Panasonic head. The Sebo heads DO NOT WORK AT ALL ON THE LOOSER WEAVE rugs!!! The circuit board kicks and shuts them off. So if you have those rugs, forget that brand it will be useless to you.
If I were you I would go with Riccar/ Simplicity. They are excellent high quality machines that are extremely durable. There were a few made abroad that were having problems which is why they have changed over their entire line in 2012 with new models that are all made in the U.S at their factory in Missouri. The overall fit/ finish, quality is superb over their previous. Riccars are very powerful. Most of the machines carry a 5 year warranty, while some carry a 3 year warranty. The power nozzles have a 6 position foot pedal activated adjustment, also push pedal handle release. Most of the full size power nozzle have a metal brush roll with 2 rows of brushes, the TOL machine from Riccar and Simplicity such as the Simplicity Gusto have 3 rows of brushes on the power nozzle. The power nozzles are very powerful with lifetime rated serpentine belts. Many would say that the power nozzle on the Riccars are more powerful than Filter Queen, and Aerus. It is also a significantly more powerful, better cleaner and easier to use machine over the Sebo D4.
Someone also mentioned the idea of a central vac. Yes the upfront price will be high for installation and unit. However once installed it has COUNTLESS benefits:
-- Household ammenity-- adds value to house for future sale
-- No emissions-- units vent outside so there is no dust emissions for the house
-- Extremely powerful-- Most central vacuums have tremendous more suction power over normal household vacuum
-- Sort of like using a canister as you're just maneuvering an electric power nozzle and hose.
--Most units are universal fit ends to utilize any number of attachments from Hoover, Kenmore, etc. You can attach the Wessel Werk MEB160 electric mini power nozzle too.
--Most hoses are 30', I would recommend getting the 35' just to ensure you won't have any problem reaching any area of your home. Utilizing the new "crush proof" style hoses they are much lighter weight compared to previous.
--Many power nozzles on the market. The Beam Rugmaster is based off the Eureka Express head and utilizes a well known VGIII brush roll. Or you can high performance and get a Riccar style power nozzle, you could even find the power nozzle that your Kenmore used, they are still on the market, and use that nozzle. Kenmore is just a name and there units were manufactured by Panasonic using Cen-Tec manufactured power nozzles.
I realize this is a lot to digest. I've been cleaning houses for 18 years, helping my clients choose vacuums that are appropriate for their households and excellent cleaning performance while being very efficient with in budget for me to use.
I strongly recommend going to your local trusted vacuum dealer to see what they recommend and what is comfortable for you to use. If you happen to have a sample of carpeting from your house that is hard to vacuum, bring it to the shop with you and the dealer can be more helpful for finding a machine.
Good Luck and feel free to contact my profile if you need further info.