Op, definitely don't buy anything with a cord - once you go cordless you'll never go back! I'm aware that sounds a bit pathetic but I'm really not joking....
The GTech AirRam is fabulous - no cord, no bag, great suction, super lightweight and easy to maneuvere (so fairly young children can easily be trained to use it! 
)
Our previous Vax had strong suction but was heavy and cumbersome and the stairs were a faff. I feel down the stairs while using it, so it had to go.......
Since we've had an AirRam four family/friends have tried it and bought one too. You've really got to try it to appreciate it.
Don't be put off by the seemingly small size of the dust/dirt compartment, the air rams it down into a little bundle so you don't have to empty it very often.
Also, the related multi-tool device is great for vaccuming literally anything - it has a light so you can see the dust you're sucking up (oddly satisfying).
Vaccuming used to be one of my most loathed housework tasks but is done much more frequently now because it's so much quicker and easier.
The customer service is really good too. When mine started making a funny noise because I accidentally sucked up something I shouldn't have
they said it was their fault because the vac should automatically stop in that situation and essentially just sent a new vac (I had to attach my old handle onto the new other parts). Can't fault that. I did do a really good job of making the noise down the phone to the customer services person though......