Here are a few things that are important to me:
The edge of the blade has to be far enough below the bottom of the handle to allow for knuckle clearance between the handle and the cutting board (the bigger your hands, the more clearance you’ll need). This usually means a broad blade.
I don’t grip the knife with all of my fingers wrapped around the handle. My index finger and my thumb pinch the blade just forward of the handle. I find that this gives my a greater degree of control and positions the pressure of my hand closer to the object I’m cutting. So I look for a knife whose heel and bolster design presents nicely rounded surfaces for all those digits to bear against. I like a thick blade, too, mostly because it provides a broader top surface to push for heavier cuts. That extra weight works against you for mincing, though.
In choice of steel, I’m conflicted. I love the ease of care of stainless, but you really just can’t get the same edge on it. There’s something very sensual about an edge that seems to melt through the goods, but honestly, I’m too lazy to pamper my knives. A great, but expensive, solution is a Japanese san mai laminated blade, with a hard carbon steel edge sandwiched between layers of stainless.