Generative artificial intelligence is fundamentally reshaping the landscape of content production in tourism social media marketing. AI-generated content, with its high efficiency and scalability, is rapidly permeating industry practices. However, consumers' differentiated responses to three content modes—AI-generated, human-generated, and human-AI collaborative—remain insufficiently understood. Drawing on Uses and Gratifications Theory and Source Credibility Theory, this paper constructs an analytical framework for tourism social media content generation, focusing on four dimensions: consumer engagement, content credibility, platform adaptability, and governance risks. The analysis reveals that AI-generated content holds advantages in quantitative engagement yet exhibits notable limitations in emotional resonance and trust building; human-generated content remains irreplaceable in emotional depth and cultural authenticity; and human-AI collaboration achieves an optimal balance between efficiency and warmth. This paper also identifies challenges including AI's misjudgment of cultural contexts, hallucinated content, privacy concerns, unequal access, and consumer dependency. This paper argues that generative AI should serve as a supplementary tool in tourism marketing rather than a substitute for human creativity and consumer trust, and that human-AI collaboration offers a viable path for tourism destination marketing organizations to achieve both scale and quality in content production.