You're best served focusing your bar prep on MBE subjects. If you understand why that's the case, you're more likely to pass the bar exam.
Depending on your jurisdiction, there can be 15 or more potential subjects tested on the bar exam. But the seven subjects that comprise the MBE are the most important to your chances of passing the bar. Here's why:
1) MBE Subjects Are Tested Twice
Obviously the MBE subjects will come up on the MBE. Duh. But they also come up on the essay portion of the bar exam in almost every state, including all UBE states that use the MEE (Multistate Essay Exam).
Usually 1/3 to 1/2 of essay questions involve MBE subjects. So sure, you may be tested on Family Law, but you know you're going to be tested on MBE subjects like Civ Pro or Crim, and they will come up a lot, on both the essays and the MBE.
So why on earth would you dedicate even half the time studying Family Law as you would studying any given MBE subject? You shouldn't.
2) The MBE is hard
Most people regard the MBE as the hardest portion of the bar exam. The questions are rarely easy or straightforward. They can be tricky, and sometimes worded in a way that guides you to the wrong answer.
The only upside of the MBE is, again, that you know ahead of time what subjects will be tested. So, you should use that to your advantage.
3) You can't game the MBE (but you can game essays)
This last point is important. The MBE is multiple choice. You cannot fake your way through it. You either know or can figure out the right answer or... you don't.
Moreover, if you miss an MBE question, you get no points. Each question is all or nothing.
Essays, on the other hand, can be gamed. Even if you can't craft a perfect answer, you can get points for an OK answer. And, if you understand the realities of how essays are graded, it's not that hard to craft an essay that reads better than it is.
4) Gaming the essays
The person who will be reading your bar exam essay will have read hundreds if not thousands of other essays answering the same question. They have a lot of essays to get through. Which, frankly, means that they're looking for buzz words and phrases.
What that means for you is this: for essays, you can get by as long as you understand the basic framework of non-MBE subjects. You have to understand concepts so you can issue-spot. But as long as your answer hits on some issues, you'll get some points.
For MBE subjects that come up as essays, this is where you can and should shine. Hit all the issues you can, get all the points you can. And it shouldn't be hard if you're putting most of your time into studying MBE subjects.
5) The big takeaway
You pass or fail the bar exam based on MBE subjects, not secondary subjects. You should adjust your studying accordingly - if you know the MBE subjects cold, you'll be in a much better position to pass.