The reason you like your sketches more is because they have gesture and because of that they have more life. You can lose that motion and movement of gesture when you go over your pieces. Part of style developement is keeping that bold freedom in mark making throughout the process.
Malcom means that in the same way you limit your steps you limit your brush to a soft or hard round for learning purposes. But that doesnt mean that you are limiting yourself style wise it just means its for understanding theory first before you explore.
The driving instructor doesnt put you in an F1 car to earn your drivers learning permit. They make you watch old videos and take multiple choice tests.
You have enjoyed your brush for half a year but it looks like you are fighting it in your rendering stage. Just try reverting to a round for a piece. Then as you go make your own round brushes with different settings that you need. Like spacing, hard edges, soft edges for rendering, size pressure sensitivity for line work etc etc. Its all about controlling your intentions because then you can control your style.
Also your lines are very sketchy. Try to have one fluid motion and intention. Try drawing from your wrist and elbow and not fingers.
Use the lasso tool to block in shapes, and select areas to paint them. Thats how your going to solve your edge problem.
good luck
