Xenfolio, Smugmug, Flickr....?

Help me decide on a Web based photo sharing and presentation site.

For me, its important that the service double as a photo backup site as well.  I see that Zenfolio and SmugMug have versions that offer unlimited storage via upload for about $40-60 a year.  Pretty reasonable, and I dont want to spend much more than this amount.  However, I have over 1 terabit of photos and have had issues with upload speed on Web based services in the past.

Other than storage, I would like the ability to selectively grant others the ability to view particular albums, download, and get prints for themselves.  I like Xenfolio in the ordering prints department because they partner with Mpix.

Anyone have any experience or recommendations with these or other services? I have been using Picasa in the past, but want something more robust w/ unlimited full file size storage as well as sharing.

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Jim