When I was in a similar position to you I tried all the photo apps I could find and just confused myself. I spent more time playing with different apps than I did in enjoying my images,
All the apps have supporters and detractors. So my advice is pick one and learn to use it, do not flit from one to another. As to which one is best? If you are new to this then pick one that friends use so you may draw on their expertise and experience. Having said that, I would skip iPhoto and pick from Aperture or Lightroom.