Are iPhone Wireless Chargers Good for Batteries?
Wireless charging is neither good nor bad for batteries; it's just an alternate way of getting the magic pixies (electrons) back into their cage (battery).  This is analogous to asking whether the interstate or the turnpike is better for your car. Both will get you to the same destination, but there are trade-offs from one to the other (i.e. the turnpike may be more direct, but they charge a toll where as the interstate is free, but it meanders around)

 
Source:  Mouser Electronics

Above is a generic block schematic of a wireless charging circuit with an external charger.  Even though the charger is "outside" the device, it's still connected into the charging circuit to the Line Drop Out circuit/chip and the battery.  What that does is regulate where the device gets it's charge from - if it's "high", it will get the power from the charger.  If "low," it will get it from the wireless coil.  But in the end, there's only one destination - the battery charging circuit.

A better question is....What works for you?


Wireless charging is slower but more convenient.
USB/Power Adapter charging is faster, but you're tethered to something.
Wireless charging has an inherent cool factor
Wired charging is tried and true
There's no connectors to wear out with wireless chargers
Wired chargers securely connect (you don't have to put it in just the right spot) connect


Basically, it boils down to what is a better solution for your personal requirements.