Not all bagless vacuum cleaners are the same. The type of separation system makes a big difference to the performance of the machine and the amount of filter maintenance required.
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.
A high wattage (input power) doesn't always mean better suction because the amount of this power that's turned into air watts (suction or output power) depends to some extent on the vacuum's design and efficiency.