Sure the Ness L300 is more money but for some of us it is worth it. One of the big things for me is that the unit is activated each step as my heal makes contact and then is lifting off the heel censor. It does not matter what direction I am going (forward, backward, a step to the side, up hill down hill....) Each time my heel comes off the censor it sends the signal to the unit on the leg. With the WalkAid it is activated on a tilt censor and this works on the angle of leg when walking forward. It is not set up to accommodate for when walking backwards, uphill, downhill or the times that the leg is not at the correct angle to trigger. For some people this not a big deal and the WalkAid is what works best for them.
My thought is that we all should find what work best for our situation and go with it. It is great that us MSer have more than one option.