AT: harder physically (steepness of climbs) , yet easier mentally. (because of the resupply options and shelters and water supply) you will learn how to deal with rain. You won't need good map and compass skills, just follow the white blazes (or blue)
PCT: more scenic, (Sierras are tough to beat), more wild, longer distances between resupply, snow travel usually necessary, less people, easier hiking terrain, harder to find water, less rocks, more experienced fellow hikers, sunshine!
But the important thing is to do one or both or them. Either one will change your life! (for the better) fh