All those are the same. If those are the only ones you are considering, then buy the cheapest one. But, you need to ask yourself some questions first.

1. Are you only going on one trip, or is this a life changing event and you plan to go on many trips afterward? Or, are you undecided, and the first trip will determine if you continue?

If this is only going to be one trip, or the maiden voyage to determine if you want to continue, then I suggest you rent a pack. If, however, you have changed your life and plan to do this a lot, then go to question 2.

2. How much stuff do you need to put in it? You won't know this until after you have all your other stuff. This is why it is best to buy a pack AFTER you have everything else.

3. What is your pack frame size? You won't know this until you go into a store that fits packs, and they have a knowledgeable person that can fit you right. If you buy a pack that doesn't fit, and you can't return it, you might as well just light a fire to the money you spend on it.