Landing Page vs Website
A landing page is one focused destination; a website is a broader system of pages, navigation and goals.
Scope
Websites support multiple audiences and tasks. Landing pages reduce scope to a campaign goal.
Navigation
Websites need navigation. Landing pages often minimize it to reduce competing actions.
Content depth
A website can educate across many pages. A landing page must provide enough information for one decision without becoming a full site.
Use both
Most businesses benefit from a website for discovery and trust plus campaign landing pages for focused acquisition.