It depends on what I'm dealing with, who I'm playing (aggressive net-bumrusher, or baseliner with netphobia), etc.
But if you ask me to pick one, running forehand, and try to hit a winner. Because chances are I've given away the court so even if squash it back, I'm either going to be pulled to another corner or lost the point on the next ball.
Though if I'm still inside the double's alley, I'll probably squash it back because I can still recover and I haven't given away the court (as much). If I'm at or beyond the double's alley, I'll take advantage of the angle and try to go for a winner (IF I can get there with enough time).
But again, too many factors to consider.