Aside from that, if you have 40 boat that weights 25,000 pounds vs. one that weighs 12,000 -- then a 300 pound dingy will affect its performance overall to a greater of lesser extent?

Under way, some boats tend to go bow down on their lines and some go bow up. Sometimes it is different when motoring than sailing.

In heavy weather, some boats are much more sensitive to waves because of reduced bouyancy if weight is carried forward -- some are not.

A lot depends on your comparison to "what" and the level of the challenge in the seaway (e.g., If you comparing performance in 2' chop/slop to flat water, you may get a completely different sense in 6' swells.

I do agree that generally, less weight forward is better than more -- but sometimes having the weight aft may keep the rudder in the water. (Think how a race boat might move crew aft with a chute up.)

Of course, EXTREMES aren't good. Putting 600' of chain in the bow of a 30' boat will not be good. ;^)