The style of handle I prefer really depends on the size of the knife and its intended use.
For example, I would hold a knife used to field dress an animal much differently then one used for whittling or chopping.
On a small knife used for fine work I like a well rounded handle that settles securely into the palm of my hand.
On a medium size knife I have come to favor a single finger grove and a slight palm swell, a rounded butt also helps.
I find this combination of features rides nicely in my hand, indexes naturally, and is a pleasure to use in a wide variety of holds.
On a bigger knife I prefer a fully contoured handle, something with an hour glass shape (i.e., a good palm swell and a flare at both the front and back of the slabs).
Of course it has to fit my hand just right; contours that are too cramped, or a palm swell in the wrong place, can ruin an otherwise nice handle.
Now for a big chopper I like a handle that I can hold loosely but securely; I find a full, well rounded shape combined with a big birds peak kind of pommel lets me have control without transferring a lot of shock to my hand/arm.
Well that's my two cents on the subject.
"If you're not living on the edge,
you're taking up too much space."
Big Mike