Some people like them, some do not. Is one way better than the other? Absolutely not. The use of briefs and phrases is a personal preference. Hard, fast rule?
Only use the ones that:
(1) make sense
(2) allow you to write faster
(3) that you know how to write out the long way.
Why is this important?
First, a brief or phrase should make sense to you in one way or another. It would be harder to commit a stroke to muscle memory that doesn't make sense or doesn't seem logical to you than it would be to learn one that you understand.
Second, the idea of a brief or a phrase is to shorten the amount of time it takes to write something out. When you are first learning one, you will naturally hesitate when you hear it because it is new. You continue to practice it until hesitation is no longer an issue. Ideally, that particular outline should be an automatic response to hearing the word or words. If it just isn't coming to you, disregard it and write it out. Remember, in higher speeds, one second of hesitation can cost you several words. The idea is for your writing to become faster, not slower or arrhythmic.
Third, you should never use a brief or a phrase if you don't know how to write the word out. The reason for this is simple: if you forget the outline, you should be able to continue writing and stroke it out. And it *does* happen like that. For whatever reason, I'll be writing and have a temporary memory lapse and question the correct outline for a brief or phrase. And if I didn't know how to write it out, I would probably sit there for a few seconds, drawing a complete blank, and listen to the testimony flying by.
For example, take the word "reluctant". Let's say you use a brief for the word because you don't know how to write it out or really have to think about it when doing so. Well, since briefs are supposed to make you write faster, there's nothing wrong with using a different outline for a word that makes you hesitate. But if you don't really know how to write the word out, what happens when the word "reluctance" comes up and you don't have a brief for that? You'll sit there and do that head-tilt thing while trying to figure out what the heck to write, all the while missing parts of the testimony.
Hey, I have words that cause me hesitation. I know how to write them out, but for whatever reason, I tend to mis-stroke it. Of course, I'll make a brief for the word. But I always make sure that I can write the word out in case I encounter it during one of my memory lapses or encounter a similar-sounding word.
And don't try to learn too many at one time. Your brain can only compute so much. Learn a few here, a few there, and keep a little book with you to write down words for which you need a new outline.
I'll step down from my soapbox now.
And as always, write clean!