It is clear by your assertion that you have NOT performed a comparative doctrinal study yourself since you believe they are not similar. Of course, you will disregard me as religiously ignorant secular liberal since it helps you to maintain your biases. The funny thing is that we secular folks actually are more knowledgeable about religion than the devoted types.
http://www.pewforum.org/2010/09/28/u-s-religious-knowledge-survey/
"Atheists and agnostics average 20.9 correct answers. Jews and Mormons do about as well, averaging 20.5 and 20.3 correct answers, respectively. Protestants as a whole average 16 correct answers; Catholics as a whole, 14.7. Atheists and agnostics, Jews and Mormons perform better than other groups on the survey even after controlling for differing levels of education."