Reliability. This is a tough one, as it requires long-term knowledge of system reliability, through thick and thin. There are many baby monitors on the market that start out excellent but tend to glitch out or completely fail within the first several months of ownership. This is especially the case for many unrecognized brand names that are saturating the market. If you're buying this as a baby registry gift the last thing you want to do is make the new parents think you cheaped out on a junky baby monitor! All of the best video monitors that make it onto our list have withstood the test of time, lasting at least 6 months, and in some cases several years at this point (like the Infant Optics option!). Another point about reliability that's worth mentioning is that most modern wifi baby monitors will keep a local connection to your app even when the internet is down. So as long as you're still in your house, you can continue streaming video even when the internet is down.
It really depends on what you feel most comfortable with. There are audio monitors that allow you to listen to any noise coming from the nursery, vital monitors that track sleep and breathing and video monitors that add sight to sound. Babylist parents overwhelmingly choose video monitors. The security of seeing what your child is up to—like if they’ve gotten tangled in their swaddle, pulled their diaper off or climbed out of the crib—can be worth the extra cost of a video monitor.