My wife worked for years with a Servicemaster franchise.  They used everything from the Servicemaster branded vacs (they had the name on them but were just some name brand painted ugly blue), Hoover, Oreck, Dirt Devel, on and on.

I asked her what she would recommend in this case and she said she wouldn't recommend any of them.  

Her biggest disappointment was the Oreck.  Boss bought a couple "professional" models.  They didn't hold up. Within a couple months they were duct taped together.  Switches broke, handles broke, there was some kind of plate on the bottom I remember had to be taped on from about the first week.  I mentioned buying an Oreck for our home once.  Got chewed on so hard I couldn't set down for days

I helped at times when someone was sick or on vacation.  Put a 50-75 ft extension cord on a vac and start out across a church or a bank  Or for me the worst was the meeting area at the extension building.  Vacuum a carpeted tool shed sometime. 

I heard her boss say one time the best luck he had with vacs was go to Wal-Mart or K-mart or the like and spend about $150 on a Dirt Devil.  It works well, has the tools on board, the company is very good about direct selling replacement parts (belts, beater bars, etc), and when it dies in a year or two you just replace it.  We're on our third or fourth one at home.  Not that they died.  Kid would go to school and eventually move to off campus housing  and need a vac.  Mom would give them hers and go get a new one.  Far as I know they are all still running.

As for the bag vs no bag argument there are advantages to both.  No bag means it has to be dumped.  That was at times a problem in contract cleaning.  Bags are a pain, but you just put a new one in and toss the old one in the trash.

But spending the kind of money Kirby and some of these other brands cost you guys are talking about?  I guess I'm just cheap!

One of these days I'll get all the typos before I post it