"okay which do you guys think is the best...S&W 686, 620, 627PC, 520; Taurus 608SS4, 627SS4, 627SH4C, 66SS4; Ruger GP100 4""
Personally, I consider the Taurus models to be a notch less than the S&W L frames and the Rugers.
Personally, I'd avoid the N frame Smiths just because they are bigger and I don't need that, unless you are talking about going to a .44 Mag. The L frames are big enough so that they will do what you want in a .357 Mag without overdoing it. Personally, I don't value having 8 shots all that much, the 6 in my 686 serve me just fine.
Essentially, the S&W 686 and 620 are the same thing. One has a full lug barrel (6 or 7 shots), the other is a half lug (7 shots). What I understand is that the 620 is actually there to fill the "K Frame Lover's" niche for those who like the aesthetics of the half lug K frames, and it is a couple of ounces lighter than the equivelant 686. I consider those to be a toss-up. Oh, and the 520 is just a different finish, but I personally prefer the stainless models from a maintainence standpoint -- YMMV, some people like the aesthetics of a blued gun, I personally don't care.
Now, differentiating between the S&W L frames and the Ruger GP-100s. Essentially, they have similar quality levels, historically at least. There is concern that the quality level of the S&W revolver line in general has suffered lately, but I can't verify that first hand -- my 686 is an old one from back in the '80s, no dash. In general the L frame Smiths are considered to have somewhat better triggers, and the GP-100s are considered to be somewhat tougher and able to better withstand a steady diet of hotter loads. In both cases, it is just a matter of degree, either family of revolvers will do what you want, a revolver from either family will likely outlive the shooter if the shooter isn't stupid about it. I consider them to be a toss-up.
"I'm leaning towards the 6" barrel because from what I understand a shorter barrel it loses power and I imagine would have more kick do to less weight to absorb recoil and it is partly for my wife who is learning. so mainly all it has to be is durable, long lasting, accurate."
Actually a 4" barrel doesn't loose all that much velocity as compared to a 6" barrel -- somewhere around 100fps depending on the load. And a medium heavy frame 4" revolver doesn't kick all that much anyway. My wife, who is recoil adverse, doesn't have any problem with my 4" 686 when shooting standard load .38's -- I haven't loaded up anything hotter for her, but I suppose that she could handle that as well. What you will notice is that the 4" model will be "handier" to carry around, 6" barrels are nice from a velocity/sight radius standpoint, but aren't the most graceful things to tote.
"also (sorry pretty ignorant on this subject) I see on manufacturer websites, magazines etc listings for 357 magnum/38 special + P...does that mean that model comes in either one, or does it mean that model can fire BOTH?"
Yep. If it says that it will shoot .357 Mags, it will also shoot .38 specials and .38 special +p's just fine. Occasionally you have to clean out the carbon rings from the cylinders because of the shorter brass, but that's just a maintainence chore. The other way is a No-No. Not to mention that .357 Mag ammo won't fit in a revolver chambered for .38 spl (+p), they did that on purpose. For that matter, that is the whole reason why the .357 Mag coming into existence -- the longer brass kept shooters from putting the new high pressure loads in older revolvers that couldn't handle the greatly increased pressures.
"my impression was they could fire both but that seems like it shouldnt be possible since one caliber is 357 and one is 38."
It is just like being able to shoot shorter shotgun shells in guns chambered for longer shells, or like shooting .22 shorts in a bolt action rifle chambered for .22lr -- it works just fine (in the case of the .22, assuming it feeds). Actually, .38 specials have a .357 barrel, and shoot .357 jacketed bullets or .358 lead bullets -- just like a .357 Magnum does.
BTW -- a .357 Sig isn't a "real" .357 at all -- it is actually a "true" 9mm, it has a .355 bore. Confusing, huh?
"if it can shoot both that would be awesome, she has shot a 22, a 9mm and a 45 quite a bit, she wants to step up and shoot the 357"
Shouldn't be a problem, just start her out with .38's and work up to the mag loads. If she can handle self-defense load .45 ACP's from something like a standard 1911, she shouldn't have any problems with a .357 Mag in a similar sized revolver.
"who knows if she likes it maybe she will claim it and I will get another new gun."
Wouldn't be the first time something like that has happened!
"anyway, considering 6" barrel because of power, accuracy and recoil."
Power& accuracy -- you have a point. Recoil -- on a medium frame gun, a 4" barrel shouldn't be a problem.
"considering stainless for durability but not a huge concern."
My thoughts are pretty much like that -- I do like the ease of maintainence of the stainless guns.
"carry but rarely and concealment wont be a huge issue"
Then you don't need a light frame or a snubby.