I am experimenting with a 14 day free trial with Smugmug. I have been using Zenfolio for years and this is what I have come up with so far. The top picture is Smugmug and the bottom was uploaded from Zenfolio. I don't see any difference. The basic rate for Zenfolio is $60 a year and Smugmug is $48. I pay $25 a year for Zenfolio and not sure why. Perhaps I am grandfathered into the original plan. Smugmug appears to be less complicated to operate however I have been using Zenfolio for so long I find it to be no problem. You can upload raw images to both sites. The above pictures are jpeg. Both programs seem to have the same features. I transferred all my pictures from Flikr to Smugmug and it was an easy process. My conclusion is, if Flikr becomes obsolete, Smugmug is probably a good alternative if you want to pay. I will stay with Zenfolio because of the rate I am getting.
Len, top one looks a little more contrasty. Smugmug has bought FlickR and us FlickR users will be moved to the Smugmug platform. I have not tried it but I would suggest staying on Zenfolio unless there is some features you need. Devil you know!