[downtown]

I think it's mostly an issue of experience. You can gain that experience a variety of ways - analyzing hands here, in SNGPT (the best way IMO), or through the school of hard knocks. The more experience I gain, the more I find that assigning calling ranges based on chip stacks is not such a bad idea. This of course is balanced by needing to consider several other factors as well that I don't need to get into, and which is not the point of your post.

I think something else that plays into the decision when it's close and you don't know is what your personal style is. For example, when SNGPT tells you that it's close either way. If you're already a winning player, your style more than anything else is what is going to affect what your finish distro looks like after 1000+ games. Typically I try to err on the side of aggression. Is this always right? No. Is this wrong if it's close? Also no. My ITM is probably fairly low for someone with my ROI, but with this style I'm comfortable with my decisions when it's close because I tend to play them the same way each time. But it could be wrong if that's not the style you feel comfortable playing. If you've got SNGPT though and you spend some time with it, you're on the right track and it will be a matter of time, study, and experience.