Let’s be honest chess.com has ten times as many players, a great web interface, a tactics trainer, an online chess mentor, and tons of articles, movies, live coverage, etc. But it’s a free to model which a lot of people find irritating and it’s a web interface which is inherently limited. Frankly the diamond membership is expensive and every other level limits your choices and puts adds in your face. I’d love to see the ICC steel some of their thunder, and their player base. 
The choice of client and its installation and learning are a substantial barrier to entry when signing up for a chess site. No question clicking connect with Facebook makes is super easy to join the enemy. The ICC should be better about advertising the things you get for that pain. And there are a lot of features that the ICC has been building for a long time that chess.com really can’t easily emulate. Some of the things that make it unique and my favorite server are below.
Chess.com is a web interface, it doesn’t have access to much of your computer’s resources, it can never offer engine analysis of your games afterwards or live watching someone else. The best they offer is to submit it to the server and they’ll get back to you in four hours with your mistakes but you can’t explore the tree on your own. Advertise this as a the tremendous learning tool that it is.
Another big advantage of both Dasher and Blitzin (Though unfortunately not the new ICC for Windows) is the ability to open multiple boards and watch several games simultaneously. I really hope this comes to the new client as it’s one of my favorite ways to watch the tournaments. Chess.com has the movies and the live coverage but you can’t watch multiple boards and you don’t have the engine at your fingertips.
The flip side of the above is the ability to share a board with multiple people. I love being able to open a board with my brother (or a coach) where we’re both able to draw arrows and move pieces around. And again we can fire up the engine to settle any disputes.
Chess variants are another one. You can’t play bughouse or checkers or loser’s chess on chess.com.
There are lots of chess engines available but the integration with the online client and the smooth installation are fantastic. Make the native programs a strength. Make the payment model a strength. Make the the things that make the ICC better than the competition obvious and people might switch.
Oh, and make chessclub.com redirect to https://www.chessclub.com. That’s a no brainer.
