I am a very stubborn and persistent fighter-backer by nature. It's virtually impossible for me to accept defeat, even when it's abundantly clear that that's really the only choice that I have. It's a fun, sexy battle for power, and one of my favorite parts of tickling.
For that reason, if I'm looking for a session where I want feel more submissive or have the session be more about the tickling than the struggle I really need to have bondage. Otherwise I get distracted by my own obsession with fighting back and can't really relax enough to enjoy the sensation.
If I'm feeling ferocious and I'm in a kicking ass and taking names kind of mood and I just want to battle it out and I'm looking for that "tactile, intimate charge" that LD described perfectly, and the actual tickling is kind of secondary, then being pinned is where it's at.
Of course, you can always start with pinning and be wrestled into bondage - best of both worlds, and my personal favorite 😉