depends on my team needs and my defense. usually I try to find a guy with high ath/decent speed/decent BH/Pass. I want them to be good at something - either really good at defense, or a scorer. I typically don't figure much on rebounding at that position. I try to make sure my SF can defend a guard (so at least one SF on your team might look more like a guard). I have seen good coaches grab super high rated defense and athletes and plug them in there (even if they can't play offense or rebound).
playing a third guard there is a good option too, but I still like to have at least one of my SFs be able to defend forwards (and guards ideally).
if you are playing a press team, you'd use the guard SF more likely. against non-press teams, you could use the less skilled BH/pass SF type. Try to exploit another teams weakness, regardless.
BTW, I think at least at PG you need to focus on BH/Pass in the core ratings.