A few of my current favorites, but if it came down to one..
It would have to be the DC17. An absolute powerhouse. Dyson set out to create a product suitable for American homes (wall-to-wall carpeting, at the time), and although a touch too aggressive for shag or looser naps, it does an incredible job. Far better than any of their other vacuums at-the-time, and still today, only a few of their models (DC28 and DC41, specifically) come close to matching the carpet cleaning performance.
It also does a shockingly-good job on hard floors, and (in my opinion) still has Dyson's best attachment setup. It featured their first wand setup where the catch released automatically, and has a really long hose (Stairs? No problem!), with a comfortable, more substantial hand grip than most of their models. It also came with 3 separate, well-designed tools.
The DC17 is also the only upright that has a Level-3 Root Cyclone pack, which is still my favorite in a bagless vacuum. It works very, very well, and it takes the filter a very long time to get dusty. They had issues originally with the gasket on the bottom of the cyclone pack moving upward (it would catch on the baffles on the dropout bin door, allowing dirt into the complex rig backwards, clogging the cyclones). They quietly fixed this, and the cyclone pack on mine is the redesigned, much improved version.
I've used the DC17 for extremely heavy cleaning (it's seen a ton of drywall dust), and it's been a trooper! I really wish they would have continued to evolve the DC17 and it's cyclonic-filtration setup, as it does such a wonderful job.
It's noisy, has durability issues, and is quite large, but I've yet to find a bagless upright I like more. Nothing can clean an entire home as quickly, with everything right on the machine, and the resulting carpet lines are gorgeous! I almost make a game out of seeing how much cleaning I can get done with this vacuum. It can thoroughly clean any room, top-to-bottom, with just what's offered right on the vacuum.
Also in the picture are my DC35, and Hoover Air. I've probably used my DC35 more than any other bagless vacuum. It's a dream for the car, and quicky spills!
The Air was one of Hoover's first really great cyclonic bagless vacuums. It has alsmost everything I love about the DC17, in a much smaller and lighter package. The base model Air has been quietly updated as well, so hopefully the issues I have with my early Air model, were addressed in later versions (I know they made the brushroll more aggressive, at the very least). [this post was last edited: 8/21/2013-21:13]
