If you can squeeze in an extra day then you can do both which would be ideal I would say.
A very unfortunate incident with the French tourist in Buenos Aires. In a way it's because the city doesn't get bad reviews regarding tourist safety that may well have contributed to the poor guy lowering his guard and having very expensive camera equipment in full view.....not recommended in any large city especially when you're on your own. I would say Buenos Aires for tourists is much safer than say Barcelona.