Cokin ND gradient fillters for landscape

With regard to the three main ND grad filters out there by cokin, as a general all purpose filter, do users out there think that the 121 soft ND8 is the best? Taking into account I like my seens dramatic and dark, generally seascapes and landscapes of tuscan rolling hills.

I have recently bought a kit of three 2, 4 and 8 and holder. So far I have only tried out the grade 4 and that seriously darkens the sky. used it at the shorline on a very sunny day with cumulus clouds begging to be shot. I would guess that using grade 8 in the same situation would make a very dramatic sky.

Cedric