If its IDPA or other organized plinking, go 4", as the rules say a 4.2" barrel is the longest concealable by the rules
Not to mention that its GREAT training!!
Perversely, I prefer at least 6" barrel for hog/deer/black bear, as .357 gets a little more speed coming out, so if hunting with it...longer is better.
Kind of why I'm saving up for a Lone Wolf Longslide conversion for my Glock 20 (10mm).
I think for overall I would lean towrds the 4" over the 6. Still accurate/handles the same-but the 4 will be so much easier to carry-less weight/less bulk and less to have to conceal. But no matter what you do what you feel is right for you-then at that point how can you go wrong...Good luck.
The difference is 2" of steel tube, just 2 measley inches. Get a good comfortable holster and neither one will give you any trouble.
BTW, the toy revolver that's been "tacti-cooled" is the most perverted, wrong, ugly excuse for a revolver that I've ever seen. A revolver is something that should be kept simple. Ug! What a horrific monstrosity! What kind of special purpose holster would one have to buy for that hideous thing? And by the time you got it out of said holster and got whatever gadgets you had attached to those rails set the way you wanted them, some fellow with an old fashioned fixed-sighted six-gun would have you killed a dozen times over.
'There is nothing new under the sun. It has all been done before.' -Sherlock Holmes
I own a 6" and love it! Good advice above. I am planning on getting either a bandoleer holster or a shoulder hostler for carrying in the field. If you are planning to carry in a hip holster then I would recommend the 4".
I love my 6" GP100 and personally if one is never intending to need to conceal a medium bore magnum revolver such as the GP100, I see no advantage at all for the 4" version. A friend of mine has 2 of the 4" guns and every time we go to the range he shoots mine more than his and is always wanting to do a trade for mine.
The main reason I would carry it is all of the rattle snakes where we hunt, hike, and shed hunt. I'm not worried about concealing it, not old enough for a CCW Permit yet. During the seasons when the snakes are out, I might load it up with some .38 #11 shotshells.