I want to keep this out of IMHO, so how can I phrase this correctly…When should one use Light olive oil and when should they use Extra Virgin type? From a culinary science perspective, is there a rule of thumb one should use?
Just use extra virgin olive oil for things like dipping bread or drizzling on vegetables stuff like that. If you try to heat up extra virgin olive oil, you will likely burn it. It has a very low smoke point.
If you are cooking anything in olive oil, use regular olive oil. Your kitchen will thank you.
“Labels such as virgin, extra virgin and pure are used to categorize olive oils according to their acidity. Virgin olive oil is the first pressing of the olives with an acidity level no higher than three percent. To receive the virgin label, however, the oil must not be further processed by heat or chemicals. Extra virgin olive oil is the first pressing of the olives with an acidity level no higher than one percent, and no heat or chemical processing. Both virgin and extra virgin olive oils are considered 100% unadulterated olive oil. Pure olive oil is extracted with heat and chemicals from the pulps, or solids, left behind after the first pressing. Virgin olive oils are said to have better flavor then pure olive oil, which is also less expensive.” Copyright 2001 by PageWise, Inc.
Basically, if you smash an olive on your forehead the grease that is left behind is “extra-virgin olive oil”, or or olive oil in it’s most virginal state. 
Salad dressings and sauces cooked at low temperatures, for a short time will benefit from aroma which extra virgin olive oil brings. It is a subtle, but rich addition to many simple dishes, including pesto sauces, and lightly cooked dishes of mushrooms, or asparagus, and the like. The pure grade of olive oil has fewer of the most volatile of esters in the natural bouquet of olives, because the processing heat evaporates them.
Cooking done at high temperatures can be done with pure olive oil, but it is easy to scorch, as noted, and the same heat of cooking will accomplish what the heat of processing did for the pure grades. Since it is more expensive, most cooks choose to reserve it for the uses which most benefit from it. For frying, and such, I recommend using Safflower oil. It has a very mild aroma, and blends well with even the most subtly flavored of dishes. It does smoke more easily than say cottonseed oil, or hydrogenated fats, but I prefer it. Both these fine oils are cholesterol free.
Tris
“It was a woman drove me to drink and I didn’t even have the decency to thank her.” ~ W.C. Fields ~