I looked at a few sites then opted for Pbase which, to me, appears more professional looking and, as far as I can see, possibly attracts the more serious photographers. But there is a small annual charge.
Not worried about people seeing my photos, at least not the ones posted there. So if you want to do a comparison have a look
crustacean's Photo Galleries at pbase.com
However, I do limit the image size to 800 pixels by 96 ppi so they won't make good prints.
Before making my choice, I looked at Flickr but had difficulty accessing the site (struggled to even find the door!) and Pbase seemed much easier. But a lot of people use Flickr so this might just be stupidity on my part. I admit to struggling with a lot of things on the internet.