I agree with some of what Larry said but not all. I had a Panasonic vacuum that I thought was phenomenal and it really was at least until I bought a Dyson. I put a new bag in the Panasonic, cleaned the entire rug in the living room and family rooms and this is after shampooing the carpet a couple weeks prior. After going over the carpet with many, many passes of the Panasonic, I then switched to the Dyson and did many passes over that. I was surprised by how much additional dirt and lint it pulled out of the carpet that I was immediately sold. And some might say the Panasonic wasnt that good but it really was a good vacuum but the Dyson was simply better.
My Dyson has a plastic container and after 10+ years of owning it, I never had a problem getting shocked. Now my dust collector in the workshop definitely builds up static on plastic, which is why I ensure I have a metal wire going from the suction end back to the dust collector.
Regarding the cordless vacuums, the reviews on the latest Dyson look intriguing though they seem incredibly expensive. Whether one would be good really depends on the user. We no longer have carpet in our house so a cordless vacuum might work well now but someone with lots of carpet might not be a good candidate.
And my parents have a nice whole house vacuum and they seem to like it and their hose is light and useful. Then again, they also dont have carpet in their main living area but do have some carpet upstairs but their central vacuum seems to work well for both though upstairs is rarely used.
So really it depends on an individuals needs and situation. Leonardo, tell us more about your situation and what youre looking for and maybe we can give some better ideas. Then again, since this is a home automation forum, youre just going to get individual experiences and in the case of Larry and I, some conflicting experience.