Why do some Audi A1 models have more horsepower than others?

I'm considering buying an Audi A1 and have noticed that some models have more horsepower than others. I'm wondering why this is the case and if it's worth investing in a higher horsepower model.

The difference in horsepower is due to the various engine options offered in the Audi A1 lineup. The base model typically has a lower horsepower while the higher-end models have more powerful engines.