I would recommend the instructions we provide simply because that gives you the most flexibility for placement. Your template may offer a module position on the JomSocial pages that you want to use. If so, feel free to use the SCLogin module and you can configure the parameters to show as much, or as little, as you want. The tag option simply lets you put exactly what you want (the login button) where you want it.
Either way works, and every site is different.
Best of luck,
Alex