You'll order them later. Write down everything that can possibly do your customer some good. Try not to prioritize as you list the benefits- that will only inhibit you. List first, order second. When writing your marketing copy, begin with your primary benefit first, then the second, third and so on down to least significant.
Features demonstrate how things are created, delivered and maintained.
Think of this section on your pages as the support system behind the benefits. Be comprehensive here because it demonstrates your professional ability, understanding and level of competence. It's a fact - longer copy sells better than shorter copy. Consumers are hungry for information, particularly if they are shopping for a big-ticket item. If they read beyond your opening headline, they are a good prospect for the product or service being sold.