DEWALT DCD791P2 18v Brushless G2 Drill Driver with 2x5ah Li-ion batteries

One of the key aspects is identifying how you are going to use the tool. It’s easy to buy more tool than you really need. Look at the torque offered by the product – the larger the torque, the more turning force your tool will have. Cordless Drill Drivers with higher torque can deal with larger fasteners or drill bits.
You should also make sure you choose a battery that meets your needs. The voltage determines the amount of power your Drill Driver can draw upon, while the ampere hours (ah) determines how long the tool can be used between charges. The most popular Drill Drivers tend to be 18v machines, because they combine power with portability.

Brushed motors use carbon brushes to transfer power from the fixed part of the motor to the rotor. This creates a reliable and relatively inexpensive motor, but brushed motors do require regular maintenance, in order to either clean the brushes or replace them as they wear out. A brushless motor, by contrast, uses a magnet mounted on the rotor to generate the power and electrical switching to perform the function carried out by the brushes. The additional complexity of the motor’s working means that brushless motors are usually more expensive than brushed.
However, eliminating the brushes also eliminates internal friction and maintenance, meaning that brushless motors offer both increased power and a longer working life. Brushless motors also generate less heat and noise and so, on balance, are considered superior to brushed motors.

That largely depends on the kind of work you’re doing. A 12v Drill Driver is fine for working in restricted spaces and for many DIY jobs, but 18v tools are becoming increasingly affordable and therefore establishing themselves as the industry standard.