A value proposition is more than a slogan. Yes, it will describe exactly why your customer should buy your product or service, but your customer should experience it on your website, at your booth or when meeting your sales team. Afterwards, your customer remembers it well, because the message is very specific about the benefits for him.
The proposition is more than words, literally and figuratively. It is clear, short, shows benefits and explains why you are better than your competitor. It is more than justified to put effort in writing down and building up a short, compelling value proposition. “I didn’t have time to write a short letter, so I wrote a long one instead.” Mark Twain got away with it, you won’t.