As of April 20th, you can now take the GMAT online in your home or office. However, you may be asking yourself, "Should I take the GMAT online or should I wait to take it at the testing center when it reopens"? If your sole criteria is doing well on the GMAT, then you should wait until the testing center opens. Below you'll find the pros and cons of taking the new online GMAT exam, and as you go through the list, it'll become apparent why you shouldn't take the online exam if possible.
Flexibility. You can take the GMAT online basically whenever you want 24/7. During normal times, you often have to reserve the test a month in advance to get a time and date you want. Now, you should be able to get a time that works for you even when you reserve your test date a week in advance.
Price. The online GMAT is cheaper- $200 instead of the €250 that most Europeans have to pay. It's also cheaper to cancel or postpone your test, and you can do so at anytime as long as your test isn't within 24 hours.
Length. With the online test there is no writing section so the test doesn't take quite as long. The time it takes to check in though may be a little bit longer (about 15 minutes). This won't make much of a difference with your score though because almost everyone does the writing section after the quantitative and verbal sections of the GMAT anyway.
Comfort. Since you'll take the online test in a location that you know, you should feel more at ease while taking the test. On the other hand, many people feel extra nervous when they have to go somewhere new to take a test.
Notetaking. This is the big one. With the online exam you can only take notes and write equations on the online whiteboard that they provide you. This is hugely inefficient and sucks up a large amount of your time on the quantitative section. You'll lose precious minutes using your mouse or scrollpad to try to write things down. The alternative is to not write anything down, but after having taught the GMAT for 10 years, I can tell you that this leads to numerous errors.
Section order. On the normal GMAT you can choose which section you want to do first. This is useful for many students because people often prefer to start with their stronger section if they're a nervous student, or they choose their weaker section if they get tired mentally before the end of the test. With the online exam, you don't have a choice. The order is quant, verbal, and then the integrated reasoning section for everyone.
Breaks. This is another big one. At the normal testing center you have two 8 minute breaks. When taking the test, you only have one 5 minute break after having completed the quant and verbal sections. This means you won't be quite as fresh on the verbal section since you won't have anytime to stop and take a breath.
Score preview. At the end of your online exam, you won't be able to see what your unofficial score is, unlike the normal GMAT. Instead, you'll have to wait at least a week for your official report to come
After taking into consideration the above, it's clear that most students will score lower on the online GMAT than they would on the GMAT at a testing center. The exceptions will probably be those students who really don't like to go to new places to take a test. For everyone else, you're better probably better off waiting to take the test under normal conditions if you can wait that long.