I suggest they're complementary.
(Disclaimer: I argue strongly that FTF is NOT the old Franklin ABC123 system. I realize Franklin merged w/ Covey. I realize that Franklin Covey probably now teaches using the ABC123 system as part of the FTF system--how could they not? But the original Covey FTF book doesn't make very much of the ABC123 system, suggesting it's one of several ways you can choose to prioritize activities in your day--if you prioritize them at all. I rant on this a bit b/c this question comes up periodically, and tends to degenerate into bashing the ABC123 system--perhaps deservedly so--without focusing on the real content of FTF. OK, /rant off/.)
FTF helps you focus on big picture: people, relationships, truly important goals. FTF asks you to focus on what's important in life and to make sure you're acknowledging those important things (people, relationships, goals) each week.
GTD, as presented, helps you handle the day to day stuff of life in a reasonably airtight system.
I, and others, combine the two strategies to sigificant benefit. I combined Covey's suggested weekly review w/ the weekly review items from GTD. So I think about key relationships and make sure I'm giving them priority. Sometimes that means I schedule an appoint to spend time w/ someone (more a la Covey); sometimes it means I add an action or project to my GTD list.
Some will argue against FTF, but I suspect their arguments--and DA's, if I read GTD right--are focused on the daily prioritization issue more than anything. I also think DACo offers some sort of seminar on "important things", which serves to make the point that nothing in the GTD model is (should be) inconsistent with FTF.
HTH.