IMO the first thing you must consider is what you will be doing with the Neck knife. If it will be for Self Defense only (and not routine cutting chores) then a smaller curved blade like the LaGriff sounds great. However, if you will be doing all sorts of different cutting with the knife and are considering wearing it around your neck for other reasons (don't often wear a Belt, disceet appearance, quick access) then I would recommend that you consider a knife with a straight blade of 3" - 3 1/2" and has a nice tight Kydex sheath. A blade that size that will stand up better to everday use.
I work on a Farm everyday and there are some days in the Summer when I will be riding the Tractor all day so I wear shorts with no pockets. On these days I wear a Dozier Pro Skinner (4" blade) around my neck. The Kydex sheath holds the knife in an inverted position very well (has never slipped out) and the knife is very accessible. It is a little bit of weight to get used to but after a day or so you really don't even feel it around your neck. Just some thoughts.