I use Photoshop everyday at work and it is by far and away the most powerful and most complete suite available. As the other guys said it’s all down to personal choice, and each tool is suited to different level of task.
The pro’s choice will always be Photoshop, however for simple tasks like cropping, photo-manipulation and touch-up any of the three will do the job.
Photoshop’s price tag is always the turn-off, but if you’ve got the money, you’ll find no better program. As I said any three of the programs will do simple tasks but with a little knowledge and practise Photoshop will do those tasks a lot better with a lot less effort.
One footnote, the learning curve is not nearly as scary as it first looks. I recommend the Peach-pit Press Visual Quickstart guides they were really easy to follow and completely invaluable to me when I was starting out in graphic design.