A lot of people have been asking this question now, what is better, online coaching or offline coaching?
Before starting with that, I'd like to talk about the Right Process required to write the GRE

FOUR STEP PROCESS TO ACE THE GRE

UNDERSTANDING WHAT IS GRE
This step is the best way to start studying for the GRE. It is very important to know fully about the exam and in what ways is the exam going to test you.

GET THE RIGHT STUDY MATERIAL
If you go on the internet, you will find a lot of study materials for GRE and the toughest part is to choose one from them as most of them are really good and so it is very important to choose the best study material according to the eay you like to study.

PREPARE
Once you have got the study material, the preparation starts. One thing that everyone says about preparing for the GRE is PRACTICE. All you need to do is keep practicing.

ACE THE GRE
After a lot of practice, the only thing one should be aiming for is, acing the GRE.

Now that I have explained the right process for taking the GRE, it is now very important to know what to choose for studying the GRE, Online or Offline?

WHY ONLINE OVER OFFLINE?

Personally, I'd totally suggest one to go for an online class over an offline class. I will be explaining why by listing out a few points below

CONVENIENT
One of the biggest advantages of online coaching is that you can study at your own convenience and pace. Study Plan is set according to you and not the tutor. Most of the applicants are either working or studying and so it becomes tough to make time to study in a coaching class. This is what makes online coaching convenient.

PERSONALISED
This is again a huge benefit for the students. Personalized training is what everyone wants. You can study what you want, when you want and at your own pace.

PERSONAL TUTORS
]A lot of students find it really difficult to study in a large group, they understand better when taught one on one. A lot of the online coaching centers, offer this feature of personal tutoring.

VERBAL SECTION GIVEN IMPORTANCE
Studying for the Verbal Section is way easier to study online than offline. There are so many apps that help students learn for the Verbal Section. They ensure that the students are good with vocabulary and also are exposed to a ton of tough words.

COST EFFECTIVE
If you have done some research, I'm sure you will agree with me on this one. Getting personalized training online is way-way cheaper than studying the same way in a coaching class. And this is one of the biggest factors for online being better than offline

These were some of the advantages of offline vs online for GRE
Some more advantages are,

Performance Tracking
Assessment

These were the reasons why I felt that Online coaching is better than Offline coaching.
But, the decision is totally upto you. If you feel you are comfortable studying with a tutor rather than an online class, that is best then. Choose according to what you are comfortable with. Hope these reasons help in deciding.
If you are looking for good Online Prep apps, there are some really good ones like Magoosh, Kaplan, etc
Do check them out.
Good Luck!