Well, a lot of the bases have already been covered here by the other two responders, but I'll throw my hat in anyway.
I agree with Castle that if this is to be your first handgun or revolver, unless you have a specific need(want) for the .44 (hunting, or like he said just like the big bores) you will probably be better served with the .357 first. And you can always get a .44 later. However, I would also like to add that if you get the .44 you might also consider the Super Blackhawk unless you strictly want DA. You can also read my range report on my new Taurus Model 44. (Don't I feel like the journalist)
As for the Python, never had or shot one. But from everything I have read on here they are either at or near the pinnacle of revolver design. That being said, their price often reflects it. One day I may own one, who knows but I don't see it anytime in the near future. If I bought one now it would be a safe queen, and more of those I don't need. Also, and I know that for some on here this is borderline blasphemy, I just have never really got into the looks of the Python. I know, looks aren't everything...but they do count to. Don't misread me anyone, I am not here to bash what I am certain is a really great gun. I just feel that I would be better served with a King Cobra, and indeed I am looking for one. I love the looks of it, and from what I understand it is a bit more "rugged" than the Python.
And, dealing with your choices for .357 Mag, if you are looking to buy new only, I would say that you couldn't go wrong with a 686, GP-100, or a SW 620. I have all three and love them all. Of course, this is assuming you are talking about a "shooter" instead of one that you can CCW as well with. If that is the case, there is the SW Model 60, the Ruger Sp 101 as good examples.
If you are looking to go used, the list gets even larger.
I know you haven't received the single definitive answer that you are probably looking for, but it is difficult for me to narrow it down to one.
As always in this situation, I will say try to lay hands on some of the guns suggested to you so far by us, and see which one feels better to you. If you can actually shoot them first as well, then that should help you decide even more.
At any rate, let us know what you decide on.