First of all, both self-study and training have their own advantages and disadvantages, so let's analyze them below.
The advantage of self-study is that you can schedule your Xi on your own time and at your own pace, without being limited by others. At the same time, self-study can exercise your self-learning Xi ability and make you more independent and autonomous. However, Xi requires you to have strong self-control and time management skills, otherwise it is easy to lead to inefficient learning or even give up halfway.
The advantage of training is that you can get professional guidance and explanations, and you can grasp some difficult points and key points faster. At the same time, training can provide you with more practical opportunities and project experience, so that you can master practical skills faster. However, training requires you to pay a certain amount of time and money, and the pace and content of the training may not exactly match your own needs. 
So, for those who want to take the HCIA exam, how should they choose?
First of all, you need to consider your actual situation and Xi learning style. If you have strong self-learning Xi and time management skills, then self-study may be a good option. However, if you need more guidance and presentations, or need more hands-on opportunities and project experience, then training may be more suitable for you.
You'll also need to consider your goals and needs. If your goal is to quickly acquire HCIA knowledge and skills, then training may be faster and more effective. However, if your goal is to gain a deeper understanding of HCIA techniques and applications, then self-study may be more suitable for you.
In conclusion, both self-study and training have their own advantages and disadvantages, and which method to choose depends on your actual situation and Xi learning needs. Whichever path you choose, it will take effort and time to learn Xi and practice to truly master HCIA knowledge and skills.