I’m going to make this kind of short.
Let me say that I’m sure SmugMug is mighty fine from what I saw but, I will admit I didn’t like that you can’t get a free account. Oh, they offer you one… for a trial for 14 days and then (this is the hook) YOU HAVE TO PAY!
Flickr does have a “pro” account that you pay but at least they give you a free account.
My judgement: Flickr wins this battle. That is, unless you want to say otherwise.