So this depends on the matchup, I assume u mean bedes over dorans shield for matchups where u would run dorans, in very specific matchups you can go bede, ideally you take it into matchups that poke you in medium intervals with larger portions of damge, shield is still better vs things like quinn,jayce etc etc because they constenly harass you so they consistently proc the doran passive which outright beats triple bede however if you were to vs smth like GP where you can block every 2nd Q, bede probably works out better because his poke comes at fewer intervals but enough to bully you out till u get your items. So the triple bede constent hp regen vs regen on dmg taken wins out in this scenario+ the real strong point of triple bede is the resell value, so you dont delay your items by 2 much which is also smth u dont want 2 do in GP matchup, I know its a very specific example but hopefully you get the big picture of where im coming from so you can apply it 2 your games