How's your block diagramming compared to theirs? draw.io caught my eye because I occasionally need to do stuff like this ( http://i.imgur.com/xs5gyDe.png ). I normally use SmartDraw, which isn't free, and draw.io looks like an interesting alternative.
CircuitLab looks more like a (nicely done!) online version of LTSpice, which wouldn't be as well-suited for block diagrams.
CircuitLab looks more like a (nicely done!) online version of LTSpice, which wouldn't be as well-suited for block diagrams.