It’s important to take your readers’ motivations into account when you’re writing copy for your website. Think about their context as they browse your site and ask yourself: Is your copy giving them what they want when they want it?
If you’re selling an expensive product or service it’s more likely that your visitors are going to be more hesitant to buy. The higher the price, the more they need to make sure your solution is right for them. In this case, give them more details. Be verbose. Answer questions before they can think of them. Make sure they have enough information to make an informed choice.
On the other hand, if you’re selling something with a low price tag, it’s more important to keep your copy short and to the point to minimize distractions. You should still make sure you’re helping people make an informed buying decision, just keep your copy proportional to the situation. People spend less time thinking about a $30 purchase than a $300 one, and your copy should take that into account.
Regardless, don’t add sentences or paragraphs to increase the length of your copy without good cause, and don’t remove anything that needs to be there. Great copy has everything you need and nothing you don’t. Now, of course, different people need different things, which means you’re never going to write perfect copy that pleases everyone, and that’s okay. As long as most of your target audience is getting what they need with minimal distraction your copy is doing its job.