The key pros and cons of Pants versus Plotting are quite straightforward. Writing by the seat of your pants lets you enjoy the creative process, going where the story takes you, and essentially 'making it up as you go along', but you can end up with dozens of dead ends, characters you don't even need, or endings that just flat out don't work because they don't make sense when compared to the beginning.
By contrast, plotting allows you to map out the work before you start, so you never sit down to write without knowing where the story is going, and you can work out story kinks before you even finish the book/story - it's much easier to rearrange elements in an outline than it is in the finished piece. Unfortunately, it can feel restrictive, and remove some of the 'surprises' that pop up when you're pantsing.
For most of my works, I've used a combination of the two. I've known the major points of the beginning, middle and end, and my writing process has been simply joining the dots, making it up as I go along to get from A to B. It lets me keep an ending in mind, but gives me enough freedom to give my imagination room to gambol about.
A while ago, I wrote a post on The Magic of 500, and I decided to revisit it to see if it would help. For a long time, I've been using the 750words.com website, and I suddenly realised that while I've thought I don't have much time to write, I've been putting in 15-20 minutes every day to write 750 words of crap. I worked out that by writing 750 words a day, a 30k word novella could be written in just forty days. So I could use those twenty minutes to do something productive, leaving my longer bouts of time free to edit The Necromancer's Apprentice. Interesting...
I wrote a Friday flash a couple of weeks ago called Contagion, and I had a few calls to turn it into a novella. I dashed out an idea for the beginning, middle and end, and just started writing. Earlier today it passed the 6.5k mark. It's going to need a lot of editing but the important thing is that I'm writing again. Aside from Friday flashes, I haven't written anything new in a long time.
So long may it continue...