i would prefer to use a hard one cos it gives u more controll. i also sharpen the pick so it has a point. i find this helps me play faster and more accurately because less of the pick has to hit the string. i use to get the clicking sound you speak of, but i found that this can be avoided by digging the pick in less.
i dont mean to sound harsh or anythin but for me soft picks where for when i started out and now i can strum properly i dont need the pick to compensate for poor technique. so i dont know particularly why veterans would want a soft pick.
anyway thats just my opinion. but i would like a pick that is multifunctionall and such. i would like one were one of the sides was like a saw blade, so you could scrape it along the pick and u would get the effect of very fast tremelo picking. and like the other side could have the material u get in violin bows. this is probably incredible unfeasible, but it would be cool.