How is SvelteKit compared to Express for backend development?

[juniorforlife]

I'm starting a new project which involves building a video-sharing platform, similar to YouTube, where users can upload and stream videos. I'm fairly new to utilizing SvelteKit, which I understand is for full-stack development, including backend abilities.
However, I'm uncertain how it compares in efficiency to a solution like Express.
Could you provide some insight into the pros and cons when considering SvelteKit vs. creating a separate backend with Express for such an application?