I choose to drift no matter what situation it is because it's just more exciting to do. When it comes to GT mode and the goal is to win and be in first place the drifts are done more moderately. I know its not the fastest, but for my personal times...I swear...it's close enough that the reward from drifting is greater to me than getting the fastest time. I get comparable times driving grip or drift, and in the end the result is just a mix of the two when playing GT mode because it's about winning and also having fun.
I try to limit the amount of countersteer and angle coming out of the apex so I can regain traction and have a decent exit speed coming out of the corner. When entering a corner, I like trail braking entrances and sliding through the apex with some to zero opposite lock, but quickly eliminating the lock once through the apex. If I'm chasing and know I can overtake for the lead soon, I'll havie fun, I will drift more just for fun. If the competition is serious, then it's do what it takes to minimize losing time and if that means less drift, then so be it.