Some time ago I've deleted almost all my pictures on Flickr and started here and on 500px.
500px works great for me, the difficulty is to choose between Flickr and Ipernity.
There are so many old contacts who are more there then here, but the design is better here, the management of Ipernity is absolutely more friendly then those on Flickr.
Only the views and links from searching sites are much less then Flickr.

So I still haven't made my decision yet. Guess I'll be uploading on 3 sites for a while, and because Ipernity is rather small, I'll won't be uploading to much pictures here, so now my contacts know why that is.