As a professional tool user, namely an electrician, I believe there is no single perfect screwdriver. Flat head screwdrivers excell at applying torque. If you need a tight fit, put in flat heads. Phillips screwdrivers excel at ease of use, with less slippage, but they cannot match flathead's torque.

Screwdrivers vary first in length and width. Length refers to the length of the shaft. Width refers to the length of the tip, on its wide side. Generally, the width of both tip dimensions are directly related. Wider screwdrivers can deliver more torque, but can be too large to fit in tight spots. Length matters in that shaft length can make a job comfortable, or simply possible. Four inches is probably the most common length. An eight inch screwdriver is a really big driver. Length and width are often related, but may be the inverse of each other. For every job, there is a tool.

Phillips screwdrivers are numbered from #1 through #4 with the width of the tip increasing with number. In my opinion the #2 is the most versatile. Not surprisingly it is also the most common. The bigger the screw {or bolt} the bigger the number used. For most people, a #1 and a #2 will get you through everything. I've had a #4 for years and used once. Like flatheads, the bigger the number, the more torque can be delivered

I have used torx head. They do a good job at both torque and finding an easy lock-up. They are rare because you must have exactly the right size for the system to work. More conventional drivers are more flexible. But a torx driver's uncommoness offers some degree of tamper proof.

Remember, for working men, tools must be carried! Most of the time, I carry five screwdrivers. One big, big flathead that is for ultimate torque. A #2 phillips . Plus a four inch phillips and square shank flathead. Square shanks are stronger than rounded shanks, but both wil probably outlast the tiip. My jeweler's flathead for electronic work, and often my stubbies, with 1 1/2" shanks.

The screw --- or bolt-- chosen by the designer determines the ideal screw driver. In addition, how much room do you have to work, I have two stubbies and plan to purchase two offset drivers for special situations. I also use several very small jeweler's screwdrivers for fire alarm and electronic work. In many situations, there is only one screwdriver capable of doing the job. So I keep a dozen or so in my tool bag besides those carried in my pouch. An auto mechanic will own even more He or she doesn't have to carry tools and faces lots of situations. A mechanic may keep dozens in his tool box.

When purchasing screwdrivers I prefer rubber handled drivers over the plastic models. They cost more, but are far more comfortable for regular use, I have a stanley that is shaped plastic with rubber bits and it is quite comfortable. A professional quality square-shank Klein or Ideal 4" screwdriver costs about seven bucks, a lot more than the Craftsmen tools on sale. Professional quality screwdrivers have a hardned tip and last a lot longer, in addition to the better handle. But you can return them, should they break.

Although they are used as such, screwdrivers are not chisels. They aren't good at chipping, and it wears them prematurely. But I've done that, in a pinch. If you want to chisel much, buy a chisel. When you go to return it, the salesman will be able to tell that you've been using your broken driver as a chisel. Chiseling leaves markes on the handle. Using a screwdriver as a chisel is an OSHA violation that workers can be fined for. That's because screwdrivers slip more, and don't offer much hand protection.

There is no such thing as the perfect screwdriver. But our basic designs are sound. As a science fiction writer I use both flatblade and phillips in alien tech. The basic designs are too logical not to be reproduced by alien engineers. All screwdrivers are flexible tools. None are perfect for every job.