They can be the same. You can lose longtail terms a lot faster. With long tail you have to compete with large sites like wikipedia or about.com that rank for everything. Longtail is not as easy as it used to be. It is still all about the big terms. If you get the big term you will get a ton of long tail terms with it. It is always best to be balanced. Never start off just doing one. Start off trying to get big terms and little terms.