I have no interest in getting into another "my knife is better than yours because ..." argument but something grabbed my attention. Somebody mentioned grip and that the Mannix is better for them. This alone is an interesting subject and could easily overcome some other perceived shortcomings of a knife, making it a "better" knife for you as compared to another similar one.
I don't have a Mannix but I do have some other Spydercos as well as a Sebenza. I have just recently got an SnG. Regardless of whether the SnG is somewhat stronger than the Sebbie or a Spyderco, I have come to prefer using it for the simple reason that, for me, it feels the most secure in my hand of any folding knife I have ever handled. Yes, there may be other knives that are more secure, but I haven't personally handled them so I don't know. Strangely, I think it feels so secure because I'm left handed and the grippy G10 clings to my palm while my fingers get a good grip on the clip. It feels like you couldn't get this thing out of my hand with a crowbar. This, apart from any other qualities, makes it, for me, the best knife.
Obviously there is no point in having the worlds best grip on some trashy POS but, when you get down to comparing similar top quality knives, that could be all the difference you need.