Hypothetical question about choosing optics for rifles

Do I have these optics on the wrong guns?

Should I put the 1-4x on the SBR due to the stiffer, heavier barrel, or the SR15 which has a lighter profile barrel, since it will have higher muzzle velocity? Both guns have FF, hammer-forged barrels.

The SR15 is super light and fast-handling with the Deltapoint, which is desirable for obvious reasons. It seems counterproductive in a way to add a heavy optic and mount to it, if the benefits of the magnification are reduced by the light barrel profile.

The 11.5" BCM sbr has a heavier barrel profile which, in the realm of the 1-4x optic, serve me better at distance. The gun is already a little lighter than the SR15, so a heavy optic doesn't seem to set me back as far as it does on the longer gun.

I haven't had the chance to shoot the guns in this configuration, so this question is mostly theoretical in nature.

http://i51.photobucket.com/albums/f3...ps8ea13016.jpg

For my intended purposes, the SBR would get an Aimpoint and the KAC would get the scope. The 16" barrel has a longer reach and therefore would get scoped.