I would personally go with the 3" for all the reasons others have stated. It's just a great barrel length. However, it really depends on what you want to use it for. If you plan on using it for hunting, then you will need to check your state/local regulations. Here in Iowa, you can't hunt with a handgun with less than a 4" barrel. And personally, I wouldn't select a J-Frame for a hunting handgun. That then brings me back to the 3" for a M60. I personally have the 2" M60. But it serves me well as my primary carry gun.

Also, you may want to check out some of the online auction/sales websites. I know buying over the internet can seem a little daunting, but I have had decent success finding what I was looking for. But for me, I like used pre-lock S&Ws & the local used handgun market isn't very good. So I am more or less forced to broaden my search scope to find what I am looking for. For example, there are a few pre-lock 3" .357 M60s (-9 through -13) on Gunbroker right now for less than $500. I would set a price point, be patient and wait until you can get one for less than that amount. It only took me a few weeks to find one at a price I was willing to pay with the attributes I was looking for.

Most of all, good luck, have fun & be safe!