Upload & Sell: Off
Having extensive experience with SmugMug both as a user for 4 years, and a customer from other photographers, I think their UI is the absolute best both from a user and a customer perspective.
Pictage is annoying as all get out. I find their proofing to be slow loading, and not pleasing to the eye. The few times I've toyed with Zenfolio, I've found the same.
Also, SmugMug has countless times, time and again, taken care of me. They're super easy to get a hold of, quick to fix issues and investigate, and they've changed for the better over the past 3-4 years, especially over the past year.
Then they announced a price hike a few months ago, I posted on their wall thanking them for their service to the industry, their passion for photography (and not just taking peoples' money), and a few days later I had a personal, hand-written thank you note in my mailbox from the screw at SmugMug. Who does that these days? They do.
I'm a happy customer, and will continue to be one.
-Galleries and subgalleries (ie. Wedding --> Josh and Dana Wedding)
-1x1 or image size thumbnails
-Auto-payments after $500 of sales (or you can request it earlier)
-Printing through Bay Photo, EZ Prints and WHCC
-Super easy to use interface (customer and user)
-Customizeable (galleries and slideshows, etc.)
-Crazy good customer service