Delica.
I have a Tenacious and 4 Delicas, including 2 of the D4 generation. I like the made in Japan Spydercos, I love the VG-10 and I like the back-lock more than the liner-lock. The feel of the Delica also works well for me.
Having said that, the Tenacious is a good knife and would serve you well if that was your final choice.
If I were you, take the D4 as a gift and buy the cheaper Tenacious for yourself
I have a Tenacious and 4 Delicas, including 2 of the D4 generation. I like the made in Japan Spydercos, I love the VG-10 and I like the back-lock more than the liner-lock. The feel of the Delica also works well for me.
Having said that, the Tenacious is a good knife and would serve you well if that was your final choice.
If I were you, take the D4 as a gift and buy the cheaper Tenacious for yourself