SaaS, develop REST or SOA architural style?

I am starting a research how architectural style I will use, to build a medium CRM SaaS, many books authors recommends use SOA, but SOA can be complex, and REST is simple style. so what is your reco开发者_StackOverflow中文版mmend?

Have any cases success with these 2 architectural styles with SaaS?

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REST, hands down.

See Chargify's API documentation. They have a REST API. They are also able to use Cucumber scenarios (automated test scripts) as the published developer documentation. This is the best way to go.