RE: Broad head and field point hits.
I doubt anyone on this site, or mostly anywhere for that matter, can tell the difference in impact over 6 grains, that would be like 1 fps tops.
However, putting an identicle weight BH will change the flight characteristics a bit. Puts more weight out front since the BH is 1-2 inches long and a FP is about 1/2 inch long. Also makes tunign more critical.
--Bob