In terms of weaponry, their about even, both possessing a vast arsenal and the skills to use it. Each one has at least one immediate advantage over the other. Bobba Fett has a jet pack and can use it for flight, and predator can become invisible. Overall, I'd say invisibility is a greater advantage, as the Jet pack makes noise, and a skilled hunter, while cloaked, need only hear it to find Bobba Fett's position. (Assuming the style of both combatants, It's safe to assume that both will eventually try to rely on stealth kills.) However, even if flight gives Bobba enough of an advantage over predator, it still doesn't allow him means to counter Predator's invisibility. So, with their weapon's about even and their advantages canceling out each other, eventually, the battle may turn to hand-to-hand combat, and there, predator most definitely has the edge. I doubt Bobba is unskilled in direct combat, but only having seen him use firearms, and factoring in the predators size advantage and rougher, likely more durable skin, Predator has him beat, though it will still be close.