For 9 mm free standing shooting I doubt case length will have any effect on accuracy. With a mechanincal rest shooting out to 15 to 25 yards if it made any diffenrance it would be so slight you would need a dial caliper just to measure the differance.
Lets face it. More times than not regardless of case length hand guns are capable of greater accuracy than most of us will ever milk out of them.
Oh and for steels more thimes than not a heavier bullet will do more than anything else. I second the 124 grain recomendation. Mine do well with Berry's plated 124 grain hollow points.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.