I personally think the 18.5" versions are the best all-around rifles you can have. But being a good all around rifle means that the shorter and longer versions will outperform it in certain aspects. With the 18.5" version, you will be good with accuracy and velocity up to 800 yards or so. After that, the 22" will have the advantage with the longer barrel and you can reach out to 1000 meters or somewhere around that.
The 16", properly set up in a Blackfeather, JAE, SAGE, or bedded into a composite stock, can hit accurately out to 500 yards with a good scope. Shorter barrels are actually better for short line accuracy. If you're shooting with iron sights only, the longer sight radius of the 22" will be easier to shoot accurately. With a 16", hits out past 300 yards using the fat XS sights, are almost purely luck.
Also, be careful about chopping a barrel. I don't know about the rifles you get up north, but if it's chrome lined, it's very difficult to chop without flaking the chrome lining. If it's not chrome lined, then there shouldn't be an issue. Just send it to a good smith that can re-cut the splines, threads and crown.
Tony.