just a clarification on when to take conqueror or press the attack ?

For me Press the attack is what the name says youre choosing this rune to be able to deal more damage to a target you focus on by auting 3 times getting bonus damage off and proceeding to deal increased damage vs that target ....but this is where my confusion lies why not just take conqueror? its easier to proc as you just need minion you get an AD boost so youre ffectivly dealing increased damage vs all targets you focus as well as converting some damage into true ... conqueror seems like a rune which helps kill squishies as well as be a tank busting rune ... i know conqueror was first made for mainly as an easier way to proc for melee targets as well as a way for bruisers to get back into the game and help beat tanks however with conqueror doing all this press the attack just feels inferior unless youre ranged although it works well on draven and MF.... so my question is this .... apart from the obvious range differences when would you take press the attack over conqueror ... cos i really cant think of when