The 20" barrel is the superlight and I think the barrel is thinner, that may be a plus or minus. I've heard some say the group grows fast with these barrels but then how often are you going to heat up the barrel coyote hunting.
If you want to do much bench shooting you might want the heavier barrel. If you're just trying to save weight I've never really thought my 22" synthetic handi was very heavy.
Tim