What's the difference? The chase and escape plots between Wiley and the Road Runner rested on the idea that regardless of your level of preparation, even the best laid plans can go awry. Wiley is continually transformed into the victim of his own plotting. He becomes a statement on humanity, a cautionary tale against hubris, against the idea that we can conquer nature through use of our elaborate technological tools. The Road Runner is a true innocent, or at least a true manifestation of the caprice of nature.
What becomes interesting about it all is that there is something of a role reversal here. The Road runner fills the role of the trickster spirit (a role normally reserved for Coyote.) Wiley denies his nature and is done in by it.
Tweety Bird is another thing entirely. He displays a veneer of innocence, but there is clearly something that is far more sinister lying beneath the surface. The threat that Sylvester poses is met with a deliberateness and, I would argue, maliciousness that is difficult to overlook. Here, it is the hunter that retains his true nature, and the prey that has become something that is frighteningly removed from what he should be.
For Tweety, the end of his interactions with Sylvester is not escape, but punishment. Evading Sylvester's attempts at predation are not enough, Tweety demonstrates a desire to cause pain and humiliation. You can see it in things like the "Oops, ran out of piddies" gag that has Sylvester plummeting from impossible heights, or in the endless glee that Tweety takes in leading his nemesis into being torn apart by the dog... again.
I thought one of the best portrayals of Tweety ever was in Who Framed Roger Rabbit. There again, the "piddies" gag was used, but in this case, Tweety was doing it to a real human being, someone for whom cartoon physics didn't apply. Instead of listening to Eddie as he pleaded, Tweety had an almost psychotic and definitely bored expression on his face. He feels nothing as he releases Eddie's last finger and watches him plummet.
I suppose we could excuse him because he is 'just being who he is,' but there really is a senselessness to his violence. He is sociopathic, and no amount of cuteness or mock surprise can hide the fact that he delights in causing pain to those who would threaten him.