Power is what matters if you're after speed and is basically a measure of the rate of work being done by the engine but it doesn't give a good measure of 'grunt'.

The example would be my motorcycle engine (CBR600) which revs up to 12/14000rpm and claims to have about 100hp. Impressive output for a 600cc engine but realistically if you threw this into a fiesta you certainly wouldn't be as fast as the TDci.....

If you want a car to pull well low down and generally just be easy to drive, you need torque, not power, as this is true measure of how much pulling capacity the engine has

Power is simply the product of torque and rpm