The main difference between Edwin Guthrie's learning theory and B.F. Skinner's operant conditioning theory is the employment of the words by Guthrie of "contiguity" and "recency".
Guthrie argues that contiguity, or the same application of an intervention of stimulus, is the most important factor to obtain the expected response, or behavior. Basically what he is saying is that if you do the exact same thing in the exact same way, the same response will be expected at all times.
Additionally, Guthrie contends that recency, or the most recent application of a stimulus (and not a past application) is the one to which individuals will react.
This theory is plausible if we keep looking at it for what it is: a theory. The main flaw is that not enough research nor experiments were performed to proof ad definitum whether the exact same response occurs with the exact same stimulus for a period of time.
However, Guthrie's theory has been very beneficial in the field of psychology, particularly for de-programming. Following Guthrie's tenets inversely, the proposed steps to the process of response do help to de-sensitize people with phobias because the correlations between the stimulus and the response can be de-constructed.
B.F. Skinner's theory is much similar to Guthrie's. However, in Skinner's operant conditioning there is still room for the fact that not all responses are identical. Moreover, Skinner believes in the gradual removal or monitoring of the stimulus because, if the subject becomes over-saturated, then there will be no effect in the behavior.
This makes much more sense because, after all, responses are a product of personality traits. No two individuals react in an identical manner because personality traits greatly vary from person to person. Moreover, contiguity is not a natural occurrence; it can only work under a research environment when a stimulus is purposely applied in a specific, rigid manner to elicit a response. Operant conditioning is modified and controlled, but it is not expected that a response that is mechanically similar will take place.
Therefore, the most applicable theory is that of B.F. Skinner