Sure it’s simpler: they’re used in two separate layers – each with its own purpose – which are consumed by separate components (and actually more, because when you send this down you’re of course wrapping it in HTTP and TCP &c.). For a better understanding of why this kind of design is simpler, and therefore better, I recommend Rich Hickey’s talk: http://www.infoq.com/presentations/Simple-Made-Easy

Edit inre “more complex compound data exchange format”: No, the point is that this should be thought of as two simple protocols wrapped one inside the other, not one “complex” format. Watch Rich Hickey’s talk. It would be a complex format if the two layers reached across into each-other, if the consumption of one depended on the details of the other, etc. But if they’re kept properly separate, that’s not complex – by Hickey’s definition anyhow, and I think it’s an excellent definition.