The purpose to the forend is to help secure barrels to the frame by holding iron that couples them. The purpose of the beavertail is to make piece excessively heavy and ugly. Just look at std grade BSS and you will see what I mean.
Straight grip must have been invented for people with loooong fingers. I will say that on sxs splinter front and straight back makes for most svelte and elegant looking piece. Of all the guns I own my ca. 1961 Model 12 feels best when fully mounted.