I suggest you get the GP100 and shoot several hundred rounds thru it right away. I suggest this because it will give you a good frame of reference to compare a Smith N-frame 45acp to, and once you get a model 25 you will probably not want to shoot anything else so you might as well get the 357 urge out of your system right away.
In my opinion, 45caliber (45acp or 45colt) and the N-frame Smith&Wesson revolver were made for each other. I have owned and shot a lot of 1911's. Colt, Detonics, Dan Wesson, Smith, Sig, even Taurus. I liked them all, and loved the Detonics Servicemaster (the commander sized model, not the tiny one). I ditched them all after shooting a model 25. I have no problem with jams when using different bullet types, and I can mix and match types in the same moon clip. I prefer the grip of a large revolver over the 1911, and the grip options are much more varied for the revolver. I think accuracy in both the 1911 and revolver is capable of being equal, but I have found the average Smith revolver beats the average 1911. You can buy more accurate 1911's, but you need to take out a mortgage to afford them.
I also suggest you buy an older model 25. They are worth the money and the search.
357mag is a great cartridge, and I really like 38special, too. That being said, I dislike the muzzle blast and recoil of a 357 (or any magnum for that matter). It seems un-necessary when a slower moving, lower pressure, larger caliber cartridge will do the job as well if not better. I hope I'm not offending you 357 fans. I simply prefer diameter and bullet weight to speed and muzzle blast. Each to his own. If you do opt for a GP100, you can't go wrong with one of them. Rock solid, and well suited to the 357mag cartridge. I'm a Smith & Wesson man when it comes to DA revolvers, but I will say that my brother's 50th anniversary Ruger Blackhawk 357 almost makes me want one. Almost. My Ruger Vaquero satisfies my SA cravings, and it's 45colt.
Good luck.