You make an important point about the distinction between control flow and data flow. They can both co-exist in a visual programming languages, but many VPLs tend to focus on one or the other.

Grasshopper [1] is very data flow oriented and functional, so you can program loops implicitly by flowing arrays, arrays of arrays, and trees along the wires, and the nodes know how to implicitly iterate over their inputs.

SimAntics (the visual programming language in The Sims) [2] (and I presume Dracon, but I haven't programmed in it) is very control flow oriented and imperative, almost like visual assembly language, and there is an implicit state (like a set of registers or local variables) that travels along with the program counter that flows along the lines between nodes.

A data flow switching "if" statement can be embodied in a data flow programming language as a node that takes three inputs: Condition, A and B, and outputs A if Condition is true, or B if Condition is false. Like "Condition ? A : B".

Or a control flow branching "if" statement can be embodied in a control flow programming language as a node that takes one input: a Condition (or it is activated by a flow of control input and the node contains a condition to evaluate against the VM state, like a flow chart branch node), and outputs the flow of control to A if the condition is true, or B if the condition is false (the road not taken). Like "if Condition goto A else goto B".

Some languages have a mix of both. Body Electric (aka Bounce) [3] is a real time data flow oriented visual programming language used for VR simulations, that primarily uses data flow switching "if" statements. The order of execution of the nodes is implicitly determined by a partial ordering of their dependency graph, and each node has an optional explicit "enable" input and output that you can use to turn on and off the execution of any node (behaving like an on-off switch type of "if" statement), and explicitly wire up the dependencies to control the order of execution (if the order of side effects is important, like for drawing commands).

Grasshopper is a good example of a successful data flow oriented visual programming language, with an excellent user interface, and a vast library of powerful features that elegantly dovetail together. I'm working on a project that uses Grasshopper for 3d printing houses. [4]

I'd caution against casually projecting anything you know about one visual programming language (like "it sucks" or "it rocks") onto any other visual programming language (and especially all other visual programming languages), because they can be EXTREMELY different! (Just like text programming languages.) And a lot of it boils down to ergonomics and user interface design, as well as the vocabulary of built-in primitives and libraries and abstraction mechanisms.

[1] http://vimeopro.com/rhino/grasshopper-getting-started-by-dav...

[2] http://donhopkins.com/home/movies/TheSimsPieMenus.mov and http://simswiki.info/wiki.php?title=SimAntics

[3] http://www.art.net/~hopkins/Don/lang/bounce/bounce.html and http://c2.com/cgi/wiki?BounceLanguage and http://www.jaronlanier.com/vpl.html and http://www.jaronlanier.com/instruments.html

[4] http://3dprintcanalhouse.com/ and this screenshot http://imgur.com/avYXU6Y from this video https://www.youtube.com/watch?v=TAoW1iA385w