Dont listen to aphilso1 he's wrong haha. The difference is a little more than "not huge" , I would call a neutron a "much heftier brother" of course he's also the same dude that got me to get a plasma Wave (Thankyou!) claiming (correctly) that it was different enough to bag a 155 plasma and neutron (correct) haha. I wish I had the patience to quote, and dig...
Seriously though the same weight (165) in neutron is an excellent complement. Little beefier, probably comparable to a full weight plasma. I really feel like the plastic makes a huge difference to the Wave.. When my 161-3g plasma waves show up I can compare to my 155 neutron and plasma. I've been wondering where they will sit. I can control my plasma for anything and I reserve the neutron for downhill stability, wind etc. It's a tight 1-2 combo with the same disc.