which dyson is best for a person with upper arm weakness, many pets plus allergies and mainly hard wood floors?

Not sure what you consider too heavy, but the DC41 is about 17 lbs. I've had no problems carrying it up and down stairs. All the Dyson's are closed systems. The cyclone technology keeps the dust and whatever else your vacuum picks up blown down into the canister, so most of the dust won't even reach the filter. Furthermore, the exhaust is on the left side of the ball and it disperses the air blowing out so well that it doesn't even blow clumps of dog hair laying next to it on a hardwood floor. All the attachments for Dyson's are universal. As long as there is an attachment hose, any current or future attachments will fit (as I've been told). I don't think any Dyson self propels but the ball moves effortlessly. I didn't look too much into the canisters but the DC41 easily gets into many of my tight corners and the bar extends to all of my ceilings. I hope this helps.