The recertification exam, by and large is easier.
Your pattern of practice could be a great advantage during the exam. For instance - using generic drugs and proper pharmacological names is always an advantage. Unfortunately, you are already many years past the completion of residency. You will forget many important pointers. During residency, you would reflexly answer that same question in your sleep.
For instance (although there will be few exceptions), an endocrinologist, pulmonologist and cardiologist go to the exam. The first one will be puzzled about the in-patient management of chest pain, the ideal stress test etc. The second person does not know what to do with somebody who has acromegaly and the third person has no clue about the treatment of fibromyalgia. These are all things that these three doctors would have a quick answer for in their second or third year - while in residency.
The good old internist who has not kept up with the times (which is so common due to the rigors of a practice) also misses many important updates.
To see the details of the differences, click