We've had numerous threads like this on here, but I'll bite.
Neither is a good option.
Guest blogging sounds like a good idea, but since it's been taken over by SEO spammers any blog that will allow you to do a guest blog post is probably a crappy blog to begin with. You'll spend a ton of time writing a post up for absolutely no benefit.
Article marketing is no better. The only point of these article repository sites is to gain ad revenue from SEO spammers who think that their articles will give them any kind of SEO gain. It's the perfect scam, and I doubt it'll die out any time soon.