First let me say that an change in speed is going to be negligible just by cutting off an inch of arrow so I wouldn't even worry about it. What is most important is how well the arrows fly. You are shooting two different arrows at two different lengths, so you're not comparing apples to apples in that respect. Were I you I'd decide which arrow you like the most and get some more in the same size and length as what you are now shooting. They both shoot well for you so it's just a matter of you picking one.

Now, as far a ballistics are concerned, anyone who knows about bullets knows that a longer bullet is more accurate at long ranges. That's why you don't see short stubby bullets shot at 1000 yard targets or anywhere else that accuracy is the goal. The same holds true for arrows, although the range is not as great. A longer arrow will ultimately be more stable in flight. And this is another reason overdraws on bows have pretty much bit the dust.

Hope this helps.