Hi Rossby,
I have 2800 sq ft of tile so switching to a canister model was a no-brainer for me.  No matter what flooring I may have in the future, I will never go back to an upright.

I don't know about your area of the  state but down here things get a little "breezy" this time of the year. (We call winds up to 35 mph breezy, anything more than that qualifies as windy) As a result I get a fair share of dust/sand unless I keep all my windows closed. I love using my canister wand to go around my house just once, vacuuming floors (including under heavy furniture and the piano), window sills, screens, the adobe room dividers, shelves, cabinets and art.

Pulling, pushing, sometimes kicking the canister around can be irritating  but I consider it to be a minor inconvenience compared to wrestling with an upright and dragging furniture around. The key for your wife would be to find one with a good power head for the carpets. Another key factor for me is a long cord. Previously, I had a self-propelled Hoover - I hated it!  Changing direction required a hard yank.
Bobbi