There are essentially two types of night vision devices and it comes down to personal preferences and in some cases particular mission requirements when it comes time to choose.
First, there is low-level light, which is naturally present and is enhanced by the device. Once enhanced an image is presented to you. Not only is natural light enhanced but artificial light as well. For example, bleed over from streetlights, moonlight, and snow reflection, vehicle lights in the area and so on would be enhanced or amplified to gain an image of the surrounding area.
Next, there is infrared, which is part of the light spectrum that cannot be seen with the naked eye. Light in this spectrum is emitted by any warm object, to include of course humans and all other mammals. Once heat is detected, an image of the heat source is presented. This is called thermal imaging device.
As stated, both types of night vision devices produce a clear image but one requires a person/object to give off heat for an image to appear. Cloaking devices can be used to counter thermal imagery and a person or object can be submerged in water, snow or covered with mud to help avoid detection.
Devices that enhance natural or artificial light would, in theory, detect a person or object that was cloaked because the low-level enhancement would present an image of whatever was within the camera’s range.
All things emit heat or thermal radiation, which are above absolute zero. However, the less radiation available means a less viewable image, in other words, you may detect something, but the image may not be clear enough to determine what it might be. Mammals radiate heat and are easily detectable unless some type of cloaking is used and often times the device will pick up the radiation despite cloaking efforts, but again the image may not be enhanced enough to determine what exactly you are viewing.
Bright light cut-off, and automatic brightness control and ones that can be handheld, as well as hands free helmet or head mounted night vision. Being able to grab your device for a quick look is ideal in some cases, while being able to mount where both hands are free are best for trekking in the dark, clearing a dark room or if you are guarding a perimeter or structure.
Older devices without a bright light cut off can cause momentary blindness if someone shines a light at your device or you happen to walk into a room and the lights get turned on.
Assume others would have night vision devices, so you cannot believe that you would be able to “sneak up” on anyone, because they may be able to see you as well as you see them. However, you would be able to see enough to hike safely, conduct night raids, or keep track of opposing forces and to gather Intel.
You need to be able to navigate in the dark without the use of lights unless you want to broadcast your location to anyone and everyone in the area.
Which type of night vision device you choose is your decision, and they do not come cheap, and if you want a quality device then you will have to step up and pay more.