both X's are very good bikes, the 1800 is a beast of a bike with tons of power. i dont know how the handling feels on it because i have never riden the 1800's. the 1300's handle pretty good, as long as the neck bearings dont wear out. then you will have to spend about 40 bucks for new ones & a few hours changing them out.
as far as the Road King, dont know how it feels either because i've never ridden it. but if it has the 96in engine on it then i know it has tons of power, because my Glide has the 96 & it will scream. when we go on long rides i'm usually cruising between 80 & 90 like its nothing. i know its alot of money but if you can find 0n 05 or 06 Road Glide or Street Glide for a good price you wont regret it.
dont get me wrong i'm not trying to pursuade you to buy an HD because all the bikes you mentioned are great bikes, but i have no regrets trading of my X for my SG. if my X handled like my Glide i would probably still have it.
"He knows the ways of the Force. He's been trained to use the Dark Xide. DO NOT Fear the Dark Xide"
2011 Harley Street Glide
2014 Fantasy Sprint Cup Champion!!!!!!