iControl REST and SOAP API

There are a lot of things to consider here. First, REST is probably faster than SOAP in many ways. SOAP is generally session based, while REST is just HTTP.

Re: http://stackoverflow.com/questions/4163066/rest-vs-soap-has-rest-a-better-performance

You also have to consider the client side environment. Whether you use Python, Perl, PowerShell, .Net, or any other language, performance is highly dependent on how that language handles SOAP services vs. REST.

What's most important, in my opinion, is not speed or performance (which REST usually triumphs in anyway), but really its flexibility. REST opens up all kinds of options that aren't available, or at least not easily available with the SOAP API. Try running a SOAP-based iControl from a cURL script. Not impossible, but highly un-fun. The industry seems to be slowly moving away from SOAP APIs, so this new REST access couldn't have come at a better time.