arydolphin
GTHC!
I'd have to say driving, because over the past few months, I've struggled with that part of the game more than anything else. It's hard to get to my goal of breaking 80 when you have 2-3 penalty shots off of the tee in every round. As amateurs, the likelihood of hitting greens in regulation goes up substantially if you are in the fairway off of the tee, so that's more important to me.
I can also say it another way: I'm pretty confident at what direction my ball is going to go coming off of the putterface, and I'm decent at reading greens, so I don't have too many horrible putting days. However, there are some days where I have no idea where my ball is going to go off of the tee, that's a really bad feeling. If I'm driving it well, I'm going to play well, it's that simple.
I can also say it another way: I'm pretty confident at what direction my ball is going to go coming off of the putterface, and I'm decent at reading greens, so I don't have too many horrible putting days. However, there are some days where I have no idea where my ball is going to go off of the tee, that's a really bad feeling. If I'm driving it well, I'm going to play well, it's that simple.