The blue manix lightweight really is light. Some people love it because of this. I believe it has a different grind than the "regular" Manix 2, too. Some dislike it becuase they view it as cheaply made. For example, I believe it has pin construction rather than screw construction and cannot be opened. It sure is light and a pretty color though. And cheap when you can find it priced right --- maybe less than $70 on occasion. I prefer the Manix 2 --- nice looker, stronger, and I like the weight. In a month or so the black Manix 2 will have S30V, not 154. That's what I would get.
(I had a Manix 2 XL. A lot of knife for the money. But too big --- primarily too wide not too long --- I returned it. Well made, milled, surprisingly light for its size.) It's a very different knife but I have an M4 Contego on order. I'll see if I like that one --- some say the handle is uncomfortable.