So....
Well, folks.....drumroll.....I chose the Simplicity Moxie. The feedback on this forum was invaluable and fascinating for me. It was truly a personal choice because they are all wonderful machines. I did end up dropping by the Aerus dealership to see the Guardian Platinum and found a few items to be less desirable for me, so I made my decision to go with Simplicity. The major deciding factors were power, cleaning and filtering ability, ease of use, features/attachments and country of origin.
I took the Moxie for a test run on my medium pile carpet and the reports are true, it really "grooms" the carpet. I can tell that I will be a little annoyed when I try to clean under furniture (because of foot lever at end of wand sticks up so high) but I am considering one of those handheld electric mini nozzles to help with this. This was my favorite feature of the Sebo - how it lays absolutely flat. I will definitely need to find workarounds for this issue.
So I will give an update in a little while on how it goes. I hope that future neophytes like me can access this thread to help them with their decision. I honestly do not think that one is exactly superior to another - it is all just a matter of preference.
I plan to take much better care of this machine than my prior vacuums! I have received several good tips from this forum and the dealers. Here is what I plan to do and if anyone has other input they may chime in:
-change bags and filters regularly as directed
-carefully rewind the cord and don't just let "go"
-do not store in garage or attic
-clean the powerhead regularly (at least monthly)
-detach the hose from the canister and wand for storage and hang hose up
-try not to drop it down the stairs

-do not let anyone else in the house use it, including spouse (a nonissue) or maid (nonissue as one does not exist)
Thanks again everyone!