The 72LGX is an impressive new Chain. It has a New advanced grind geometry, (Just look at the pictures and you can see the new tooth has an improved angle) significantly improves out-of-box sharpness, substantial speed improvement in boring and bias (undercut) modes. Look at the cutter here:
Compare it to the Old 72LG,
Here are some other improvements as well as their other features:
StabL-Link™ drive links, dramatically increase stability in the cut, (patent pending) ( It sure looks different and I can see where the larger drive link will help in keeping the chain straight as well as it fits the sprockets better.)
Blued cutters, provide improved grind consistency, dependable chain to chain performance, superior corrosion resistance
Tumbled parts, improved joint articulation, reduces friction and stretch (I noticed it's easier on your hands, the smother finish which should mean less drag through the cut.)
Offset ramp-shaped depth gauges reduce roughness, helps prevent cutter from diving into the sidewall of the cut
Clean ground gullets, increase chip flow and evacuation
LubriLink™ tie straps help keep oil where it's needed - on the chain
Top-plate witness mark makes accurate sharpening easier