Plotter or Pantser. Which are You?

I’m in a dither, but it’s my own fault. 
I can’t seem to get involved in my current story, even though I have a cute guy on the front cover, a cover which, I might add, I won. I’ve re-written my introduction several times but I’m still not happy with it. 
The thing is, I know what my problem is and how to fix it.
I recently read an article by Derek Murphy, who says, ‘I had trouble getting through a whole book until I learned story structure and plotting—and after I learned it I’ve found it much easier to produce fiction that sells, much more quickly.’
Many writers do ‘write from the seat of their pants’ and the story unfolds for them as they go. They enjoy letting the characters drive the plot along and may even justify it by saying their characters create the dialogue and therefore the situation. This may work for some genres such as romance, but I write epic fantasy and if there’s one thing readers like are the subplots, the twists and turns, the secondary characters who also have their part to play in the overall plot.
When I wrote the Bethloria series, which has seven books in total, I semi-plotted each one out. I had a vague idea of where each story was heading and who some of the characters were going to be, but it was only a skeleton of an idea and not fleshed out. 
It had holes. It had weaknesses. 
The thing going for it was that I knew my created world inside out. I’d smelled the untaming rot in the trees, seen how its dying forests appeared, felt its icy weather, experienced the dungeons and dragons and demons that I forced my main characters to experience. Thank goodness I was able to weave all the loose ends together at the conclusion of the series.
But it could have ended up in a great big mess.
On the whole, as a plotter, I tend to write better-crafted stories without gaping plot holes. I generally have loads of page notes which I can incorporate and create a gripping tale. When I’m writing from ‘the seat of my pants’, dialogue takes over and characters hijack my already flimsy plot, more flaws tend to appear in the actual story whose direction I have little idea of and I have loads to correct once the manuscript returns from my editor. 
I had a friend once whose junior fiction stories were snapped up by a publisher. They signed her up for a series and my friend suddenly had deadlines, which stressed her out no end. She also worked and had a young family to look after and the only time available to write the series was late at night when everyone went to bed. She decided to write the stories by the seat of her pants, thinking she’d get them over and done with quicker. The publishers detected glaring holes and other problems in her stories. In the end, they rejected them. My friend had made more work for herself because she had to rewrite large sections of the stories.
‘I just don’t know what to write,’ she moaned. ‘Or what’s going to happen next.’
Luckily, she had a light-bulb moment and decided to plot out her remaining books, which was when she began to write faster and with a clearer direction. Plotting essentially gave her a map from beginning to end, enabling her to churn out six books.
One famous plotter is James Patterson, whose extensive outlines read like little stories on their own. Sounds like hard work to me. On the other hand, Stephen King is a pantser and enjoys stressing out his characters to see what transpires. Seems to have worked for him.
So, which are you: plotter, or pantser?