Imgur is great for simplicity re: sharing images on websites/forums, but Flickr is much better for photography and sharing you photos with friends and family. Imgur is kind of like twitter - more about random images/screenshots and then getting people to comment, frequently in text-speak. Flickr is a place to collect and display your photos (and share them) or join subgroups that focus on different photography themes. Very different websites.
I can't see why you'd do imgur if you already have Flickr, like the OP.