I do both, I uses patterns sometimes and others I either use a picture I like to make it up as I go, depends on the mood I am in. It really depends on you whether one way is easier for you, and what you are looking for. Most of the mistakes that I make when doing my own is the way the seams are pressed, of course I hit the same issue if I make to many changes to the pattern that I am using. even using a pattern I tend to draft out some things, it makes it easier to follow for me
I have used the Dear jane software which is done by the same company and for the most part if you know how to run a basic program it isn't to hard to do, they also have step by step instructions for those that are good at using them,