Slow and heavy wins every time. The bow is quieter, broadhead flight is better, wear and tear on the bow is reduced, KE and momentum is higher initially and is retained better over distance.

You would be surprised at how little trajectory difference there really is when comparing light and heavy arrows out of the same bow.

For instance...
A 350 grain arrow shot at 340 fps and sighted in at 20 yards will drop 12.6 inches at 40 yards. It will start out with about 90 foot pounds of KE.

A 500 grain arrow shot at 290 fps and sighted in at 20 yards will drop 17.4 inches at 40 yards. It will start out with about 93 foot pounds of KE.