Factors to consider when purchasing a screwdriver:
Type of tip:  Common types include flathead, Phillips, Robertson, Torx, and Hex-Head
Tip size:  Phillips and Robertson screwdrivers typically come in three or four standard sizes, whereas flathead, Torx, and Hex-Head have a broader range of sizes.
Length of the shank:  Shank lengths can range from a few inches to over a foot.  Longer shanks offer greater torque, but limited space may require a shorter shank.
Handle size:  Handles with greater width can produce more torque but may be more challenging to grip.
Handle grip:  Handles coated with rubber are not only more comfortable to grip but also offer additional electrical insulation.
Measurement standard:  SAE uses imperial measurements while metric measurements are in millimeters.
Price:  Screwdrivers with shafts made from high-quality alloys are pricier than those with standard steel shafts, but their durability and reduced risk of bending or stripping screw heads often justify the expense.