For me, the level of difficulty is ranked as follows:

FAR -> REG -> AUD -> BEC

FAR exam was also the hardest. I didn't have enought time to finish the second simulation and most of the questions on the mcq were very tricky. I don't have any tax or auditing experience, which made preparing for REG and AUD difficult but I was lucky to get relatively easy mcqs on REG. AUD was also tricky but had enought time to finish the exam. My shortest prep time was for BEC, which was less than 5 weeks. The cost part was difficult to grasp. The exam was fair.

Here is what I think (and my grades may not reflect this):

FAR – REG – AUD – BEC

FAR - There is just SO MUCH information in FAR that it can be a bit overwhelming. The items I thought would be tested heavily were barely even tested and the items I thought would not be heavily tested were. I think the key with FAR (as with all the sections) is time management. If you do not manage your time wisely then the chance of you failing goes up drastically. You need about an hour to complete each sim (2 hours total…or atleast 1 hour and 30 minutes). This is the only partof the exam where you can show a human being that you understand the concepts (ie. Written communication…this part is crucial and you must spend about 15 – 20 min on this part…and don’t forget spell check!). I believe the rest of the sim is graded by a computer but still…this gives you the chance to show the grader that you are able to take a client’s situation and turn it into a finished product.

REG – I work on the tax side but this exam isn’t easy…even for us. It is very detail oriented. This was the section I was most concerned about (I suppose because I did very poorly on it the first go round). Again, leave adequate time for sims.

AUD – I’m not an auditor. My mind doesn’t think that way. This exam is a lot of memorization but it also is about understanding what they are asking you for. Sometimes it can be hard to tell. This is the first section I passed and was utterly surprised that I did it, ha.

BEC – I’m not saying this is the easiest one b/c there are no sims (I actually enjoy the sims). I think this is the easiest section because it is the most manageable. When you break down the exam into the different sections there really isn’t that much information to go over. I studied for this exam for maybe 1 – 2 weeks max. The key is practice practice practice (this is the key for every section). Work MCQ until your eyes bleed. It is extremely important (in all sections) to work the released multis. These are questions that have been on the exam before. If you can answer these correctly then you know that you are on the right track.

Hope this post was somewhat helpful to someone.

FARE

Studying - Tons of material to know, that means they can literally ask you anything. Tends to be more conceptual with some moderate amount of memory involved. 

Day of test - Time wise is fine because is 4 hours, as long as you pace yourself shouldn't run out of time.

REG

Studying - Tons of material also, but not as deep as FARE. Tends to be more memory (Especially exception to tax codes and business law). Not as heavy on concept.

Day of test - Definitely a pressure cooker for an average person. 3 hours can drive you nuts especially after you finish all MC and they drop you with a long simulation. Heavy time pressure.

BEC

Studying - A lot like Reg but with fewer chapters to study. Is a mixture of memorization and concept.

Day of test - Expect the unexpected because there are a wide range of questions. It tends to be also pretty tricky, so read things carefully. Time is definitely not an issue.

AUD

Studying - Heavy concept and moderate memorization. Material is light compared to other 3 parts (My opinion at the very least).

Day of test - Tons of time. Nothing really out of ordinary

Juristidction

So which one is hardest and which one is easiest? Following is rank in terms of hardest:

1) FARE - Per above, this test has tons of material for you to learn, by the time you're studying the back end of stuff you may have forgotten some of the stuff from the beginning. This part requires to you to constantly reinforced the stuff you learned from the beginning. In addition, they can literally ask you anything on test day can make this pretty stressful on test day.

2) REG - Close number 2. What makes REG a little better is that you can beat this test if you can memorize things. For FARE it does not work because it is more conceptual. FARE requires you to understand conceptually and memorizing certain aspects. REG on the other hand is more memory base that is why I slot it as number 2. Only thing that really makes this test a nightmare is the 3 hours.

3) BEC - This test really reminds me of REG but without the simulations and less things to memorize. However, most people think this is the easiest section. I'd have to disagree because this test has no simulations, that means the Multiple Choice will either make or break you. Hence, no simulation to make up for you doing bad on Multiple Choice.

4) AUD - This is probably the easiest section. Simply because each chapter in the book is sort of interrelated to each other. It is very conceptual base. So if you can follow a chapter it can help you on the next. The material is a little lighter compare to the other 3. In addition, the 4.5 hours makes test day less stressful.