The Phone Needs to be in Constant Touch with the Wireless Charger 

The main drawback of wireless chargers is that it has to stay on top of the charging pad to continuously charge. But with a cord, you are at least free to move around the diameter of the cord.  

Expensive 

It's expensive to purchase a wireless charging pad, especially when new smartphones come with a corded charger in the box.  

Inconvenient

One of the major disadvantages of Wireless Chargers is that they aren't great at providing the quick bursts of charge you need if you're on the move. This is because it takes longer to charge than your wired charges and being on the move constantly hampers the speed of charging.

Speed 

The kind of phone you have and its power compatibility can make a major difference in how fast and efficiently a wireless charger can power it up. The speed of charging can be measured under three main categories- 7.5 watts (W), 9W, or even 15W. Sometimes software plays a part in the speed. Right now, 10 watts is all you'll need if you want to get the fastest possible wireless charge out of your device, which typically translates to full recharge times in the roughly three-hour range, but that can vary.  

Power 

Compare the wattage speed of the Wireless Charger with the specification listing for your standard wired charger, and then check if hat speed is good enough for your phone.  

Qi charging 

Qi charging is the universal standard, so if you have multiple wireless-capable devices, you can use the same charging pad without any issue. Make sure you invest in a Wireless Charger that supports the Qi standard. The efficiency of Qi charging is still lower than cable charging, so it takes more time to charge your phone through a Wireless Charger using the same amount of power.  The most popular wireless technologies now in use rely on an electromagnetic field between two copper coils, Qi wireless charging technology as it currently stands can transfer up to 15 watts of power via wireless induction. 

Brand    

As the phone you are charging is usually expensive, it may not be worth saving on the last bit of money to buy a cheap wireless charger. If you're in doubt, stick to brands with a good reputation for charging gears. 

Warranty 

Warranty is very important when it comes to gadgets and should be checked before investing. A Wireless charger should come with a minimum warranty of 6 months to a year. 

Price 

The price of a Wireless Charger may vary between USD 11 to USD 45 depending on the brand, watt and performance.