A very similar question came up a few days ago and there was some rumbling about recomending a 44 mag revolver for someone who wanted a 2-in-1 defense/hunting pistol. But, since all you want yours for is to hunt, I doubt there will be any controversy in recomending you go with the .44 mag over the .357.
You'll be limited with the .357 as a hunting gun. I'm a firm believer in using cartridges for their intended purpose. An example is hunting with the 7.62x39 round. The cartidge was never designed for hunting. It was designed as an anti-personnel round at short to medium ranges. Granted Corbon and some others have stoked this cartidge up with a 150 gr. bullet and some extra punch so that it will probably do as a hunting caliber on smaller game. But at the end of the day, you're jerry rigging a cartridge to do something it wasn't designed to do. Why use a 7.62x39 when you can use a 30-06 or a 308?
That's how I feel about the .357 for hunting. The .357 was designed as a man-stopper, not a game taker. Granted, you can get a 180 grain bonded core soft-point that will probably do the job with good shot placement. But why use a .357 when you can use a .44 mag (which was designed for hunting)?
But, if you do go with the .357, the Ruger GP100 is a fine choice. Personally, I'd get the 6" barrel for hunting.
However, if you're open to the .44 mag, and you like Rugers, I'd check out the Super Blackhawk (Single Action) and the Redhawk (double action). Both tough guns that will handle a lot of 44 mags.
Good luck.