Since REST uses standard HTTP it is much simpler in just about every
way. Creating clients, developing APIs, the documentation is much
easier to understand and there aren’t very many things that REST
doesn’t do easier/better than SOAP.
REST permits many different data formats whereas SOAP only permits
XML. While this may seem like it adds complexity to REST because you
need to handle multiple formats, in my experience it has actually been
JSON usually is a better fit for data and parses much faster. REST
allows better support for browser clients due to its support for JSON.
REST has better performance and scalability. REST reads can be cached,
SOAP based reads cannot be cached.
It’s a bad argument (by authority), but it’s worth mentioning that
Yahoo uses REST for all their services including Flickr and
del.ici.ous. Amazon and EBay provide both though Amazon’s internal
usage is nearly all REST source.
Google used to provide only SOAP for all their services, but in 2006
they deprecated in favour of REST source.
It’s interesting how there has been an internal battle between rest vs
soap at amazon. For the most part REST dominates their architecture
for web services.