one of difficult vs one of the difficult

Some examples from the web:

• So the paths to sin are manifold: the paths to holiness one, and that one of difficult access [Grotius]. One drop of filth will defile a vase of water: many drops of water will not purity a vase of filth [Moore]. Haggai 2:13 Additional Commentaries.
• Legal sanctity is not so readily communicated as legal impurity. So the paths to sin are manifold: the paths to holiness one, and that one of difficult access [ Grotius]. One drop of filth will defile a vase of water: many drops of water will not purity a ...
• process as one that “is nearly always one of difficult personal discovery, of slowly and painfully appreciating a personal consistency that cannot be explored through routine socialization mechanisms” (320; emphasis in original). In this way, my ...
• Israel's future is not one of blind faith and obedience to God's will but one of difficult covenant partnership, of wrestling with their own inclinations and doubts in the face of a mystery which will not fully reveal itself. Covenants do not necessarily ...

Some examples from the web:

• One of the difficult scenes in Guardians of the Galaxy to create was the Orloni Pit scene. In the scene denizens of the Boot of Jemiah each bet on an Orloni (each of the Orlonis have a different color swatch on them). The larger F'saki is placed ...
• Finding a balance is one of the difficult issues in academia. It was very difficult if you didn't know your way around or didn't have access. Control is difficult, because the fungus can survive in the soil for years without a host. It has been a difficult ...
• Finding a balance is one of the difficult issues in academia. It was very difficult if you didn't know your way around or didn't have access. Control is difficult, because the fungus can survive in the soil for years without a host. It has been a difficult ...
• One of the difficult areas and indeed one of the frequently examined areas in the sphere of consideration is the issue of past consideration. To recap, let us revisit the definition of consideration provided by Justice Lush in the case of Currie v ...