Having to do only one type of stitching restricts me too much. Sometimes i need to stab but when I get the rocking stitch going, I enjoy it more and I can achieve smaller, more even stitches...which took yrs of practice.
For me, the trick to rocking is with the first insertion of the needle...it helps me if I point my needle straight down vertically into the quilt poking my underneath finger which has elevated the quilt upward and then push slightly forward on the underside then bring the needle up at a sharp angle with my thimble on my right hand... Which makes the first stitch.
Having the right needle is an issue for me....if it is not working for you, try as many as you need to to become comfortable. I favor Betweens while some others like Sharps.
When I stab stitch, my needle is more parallel with the fabric.
I have a friend who stitches neither method...just straight up and down stitching. She wins blues and best of show at the County fair every year.