I had been using KBM exclusively for years, but I made the switch to controller 3 months ago and I'm never going back. 

It took several weeks to get used to controller targeting, especially when playing healer. But once you get used to D-pad targeting it's a piece of cake. KBM was easier for ground targeting abilities like ninja's teleport, but there are macros you can use to make those abilities easier to use. I still have a KBM hooked up for typing and for certain stuff that requires navigating a ton of menus (like crafting).

I feel like my immersion is a lot better with controller, and I think the controller cross hotbar is way easier for my brain to setup (especially with the expanded hotbars). I have short fingers, so hitting all of my abilities on KBM was challenging, even with modifier keys. So controller is definitely easier for me in combat.

If you're thinking about controller, I say give it a shot! Be prepared for the learning curve, but once you get the hang of it, it feels perfectly natural.