I prefer quarter sawn for some and flat for others. In part it depends on the woods, but largely for figure.
For closed handles, it doesn't matter too much, even though my preference is between rift and QS woods.
For open handles, the biggest give a heck is how the grain runs down through the bridge. The bridge is the part which connects the handle proper with the cheeks.
The picture below is of a handle paid out on some Cocobolo, chosen for it's strong grainlines for the picture.
Ideally, the grain would have run at a steeper angle, but that was the board I had for use at the time and is more than adequate.
On this completed saw, you can see how the grain is running a little steeper through the bridge:
On a closed handle, those grain lines can run straight or angled. Really doesn't matter as regards strength, but I like them to cross the handhold portion of the handle at an angle as this one does:
Thickness is another thing. For an open handle I like to begin with a hair thicker than 1", for an open handle it can be thinner. Some open handle styles when replicating vintage saws we finish off about 13/16" to 7/8", but across the hand hold is wider when the thickness drops. It's all about those two dimensions as regards comfort.
Take care, Mike
Wenzloff & Sons Sawmakers