I too have a fairly short approach... I changed from a long approach in September because the short approach kept my motion more condensed... I lost a little speed, but only a half a mph or so, which you just adjust too...
So in my dealings a short condensed approach will be slightly more accurate and easier to maintain form through, while a longer approach will mean slightly more speed and revs...
Even then, the difference is pretty much negligible as I have seen excellent bowlers with drastically different approaches...