What percentage of your customers are "bad" but not in default versus good? In my experience, a good lending portfolio will have over 90% good customers, less than 3% in default and the remainder with minor arrears. How does the gini of your "indeterminate" customers compare with your good customers? I would expect to see a higher gini for indeterminate's as these are the most likely to go into default.
Use this tutorial as a handy guide to weigh the pros and cons of these commonly used machine learning algorithms.
Find more tutorials on the SAS Users YouTube channel.