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.
The nozzle design in particular on both cylinders and uprights can have a big effect on dust pick up performance and although not yet available, it will soon become commonplace to see a Europen IEC test standard. This will reflect the percentage of dust the vacuum cleaner picks up.
