I have always liked the leather bags on the Road King Custom
Just so happens that I have a Custom with leather bags. I personally would trade them for hard bags in a heartbeat and will get them if/when i save up enough cash. My "leather" bags lock so they're even there. I want the hard bags based on looks alone.
On the RK, definitely Hard Bags. The leather ones look better on the non touring models. You wouldn't want your Cadillac to look like a Pinto would you?
I have hardbags on my 09 ultra,leather on my 86 fxwg. I had Boss bags(36 plain) on my 05 fatty the best of both worlds for me. Not cheap bags but well worth it.
Question is, What do you want on YOUR bike? I had leather bags, someone when through them while the wife and I were in the store. I now have hard bags, which lock, and like the look.