Define “most suitable”.
The goal of the screwdriver design isn’t “which will stay cleaner?”.
In automotive, I rarely encounter Phillips head screws. Used to be that entire interiors were held in place with trim head Phillips screws. For interiors (assuming low torque, low corrosion), the best screwdrivers are those you can spin the fastest. I like Klein style for that. Grease is not a factor when removing glove boxes, etc.
For engine bays, I see Phillips only occasionally, and when I do, they may be stuck stuck stuck. In those instances, I want something that can deliver torque. That’s what Instincts were designed for and excel at. The handle shape, even when coated with grease, still provides good torque transmission.
But of course this depends on the shape of ones hand and grip strength. I think instincts offer a mechanical advantage, helpful for folks who suffer from arthritis, hand fatigue, or don’t for whatever reason have hands of steel.
In my opinion, Snap On’s hard handles offer a reasonable mid point. Their popularity with pros world wide has earned their reputation. The blades are excellent, handles are easy to clean. Mine are 30yrs old, worn smooth from years of use. Only criticism: I find them a bit slippery sometimes. With gloves on, no problem.
I recently rebuilt the head of my milling machine. There were lots of straight slot and phillips screws. Mucky to disassemble, super slippery greasy reassembly. I used hard instincts. You can wipe them clean with a paper towel. And clean them spotless with non abrasive hand cleaner. They worked great for me.
So a better question might be, “when your hands are greasy, which screwdriver handles still provide enough grip to be functional, I.e. deliver torque?” My answer is Instincts. It’s not a beauty contest.
