Velocity will be slower out of a 2" barrel, but enough to matter? Maybe not. As far as accuracy, I've had some 2" guns that were more accurate than 4" guns and some 3" more accurate than 6". On average, longer barrels are more accurate, but individual guns are defying the law of averages all the time.

Something to keep in mind, though. I've been told that there are places where 20 or 25 yards would be dubious as "defensive" handgun use. Just what I've been told. I think 2" revolvers are accurate enough for most defensive applications.