For my 2 cents, I say the 17 is better! Not exact comparisons but I draw or shoot faster with the 17 than the 34. Of course I used a Gen 3 34 my first year in USPSA, and a 17 Gen 4 in my third year, so not all may be equal. Most of our targets are within 15 yards, and the shorter slide seems to be faster for me. If you have to take alot of long or partial cover shots, the longer sight radius may help you out.
Either way shouldn't be more than a few % difference in your stage points.
Addict