Is Having a Monitor Arm Worth It?
Competitive gaming is an ultra-competitive field where people will take whatever advantage they can get, be it in the form of hardware (gaming tables, monitors, mice, mouse pads, etc) or software (latency, custom resolutions, custom crosshairs, higher FOV, etc).
Some of these choices however give no real competitive advantage but do improve your overall experience and comfort. This is the case with buying a monitor arm instead of using the included stand for your monitor – it allows for comfort and adjustability but gives you no real advantage in games.
Health
So if there is no advantage to be had, why do people still buy monitor arms? The answer is quite simple and it has to do with your posture and health while playing games and doing PC work. To maintain a healthy posture you need to keep your monitor at a certain distance and a monitor arm makes those instant adjustments extremely easy.
With a monitor arm, you can take into account the monitor size, the size of your table, and what would be a comfortable and healthy position for you to game and work in.
Adjustability
Even if we completely ignore the health benefits a monitor arm offers you unlimited movement and adjustment in a 3D space in front of you. This cannot be said about monitor stands since the cheaper ones often do not even offer tilt options.
If you have a good monitor but the stand offers no adjustments, buying a cheap monitor arm will change the way you use your device since now you can place it in the exact spot you need it to be (even if it might lead to a not-so-healthy posture).
This is also valid when you have multiple monitors with different stands that offer different degrees of adjustability leading to a setup that has the monitors all over the place. Having a monitor arm will allow you to have identical settings for all your monitors and if needed instant adjustments to said position.
Less Clutter
If you hate when your table is cluttered or if you have smacked your mouse into your monitor stand a couple of times while gaming you would understand the appeal of having your monitor suspended while using it.
A monitor arm will allow for unlimited movement around the monitor since now you do not have to account for the (usually) large base that is needed to keep the monitor stable. The monitor arms will also allow you to mask your cables going to your table and allow for a clean minimalist look that would be hard to achieve otherwise with multiple stands on your desk.
Conclusions
In short, you do not NEED a monitor arm (especially if your monitor comes with a nice stand) but it will definitely be a great quality of life improvement both for your health and the aesthetics of your setup.
Be it because you do not want to look like a shrimp while gaming or because you need more mouse space, a monitor arm is never a bad idea.