The main differences between REST and SOAP style Web Services are:

a) REST assumes point to point communication model and is not usable for scenarios where clients go through several intermediaries. SOAP is designed to handle distributed computing environments.

b) REST requires minimal tooling/middleware, only HTTP support is required. SOAP requires significant tooling/middleware support.

c) REST does not enforce any constraint on payload. SOAP services must use SOAP formats for payload.

d) REST is tied to HTTP protocol, SOAP services are protocol agnostic and can use various transport protocol like HTTP, SMTP.

e) SOAP services support a large number of supporting standards for security, reliability, transactions etc.

f) REST is more lightweight and can be implemented using any tool leading to lower learning curve.

g) REST uses URL based access, whereas SOAP uses message based access.