i like to have both options, because around town, a neck knive probably isnt going to go over so well, but if i am outside and bundled up, i prefer the necker setup because when i am bundled up, it is usually difficult to get into my pocket. maybe, to give the option of both, for leather you could just put two holes at the top of the sheath so it can be used for either pocket or neck carry. and on kydex, just make two holes at the bottom for the same reason.
put i think, if i always had the choice between carrying it in my pocket or on my neck, it would usually end up in the pocket, although it would stilll probably see alot of neck time under certain circumstances.