There are some specific characteristics of certain popular transports that are worth noting. These include the ubiquitous protocol of the web, HTTP, as well as SMTP and "raw" TCP/IP. Other common protocols such as FTP are also quite usable in certain situations.
Choosing which transport to use is not easy. HTTP and HTTPS are almost universally available. Corporate firewalls are normally open to HTTP traffic, though some do look at the payload and distinguish between normal web browsing and serving and distributed computation of the sort supported by SOAP. Server software supporting HTTP, such as Microsoft IIS or Apache, is highly developed and extremely reliable. Many development tools and SDKs are available to decrease the development effort.
On the negative side, the request/response model of HTTP does not support asynchronous notification very well. Some applications depend on the client being notified when certain conditions are met, such as changes in traffic or road conditions. If HTTP is used in such cases, the application of HTTP imposes some extra burdens on both client and server. There is little practical experience with the current crop of asynchronous add-ons in the connection-hostile mobile world.