Although many people aren't aware, upright and cylinder vacuum cleaners were originally designed for different purposes. Upright vacuum cleaners were designed for vacuuming carpeted floors in cooler climates (such as the UK) while cylinder vacuum cleaners were designed for vacuuming hard floors in hotter climates (such as Spain). As a result, not all cylinder vacuum cleaners come with powerful rotating brushes.
If you suffer with asthma or a dust allergy, the filtration system should be an important factor to determining which vacuum cleaner you'll buy. This is because the filtration system will determine the size and number of dust particles that'll be in the air when it is exhausted out of the vacuum.
The capacity of the vacuum cleaner's dust bin or bag will essentially determine how often you'll need to empty it. If you have a large house and you don't want to be going back and forth the bin, it's worth investing in a vacuum cleaner with a bigger capacity. That said, if you have trouble lifting or manoeuvring a vacuum cleaner, bear in mind that the bigger the vacuum cleaner's capacity, the heavier it'll be.