Which is worse, dying from a gunshot wound, a knife wound or a flesh eating bacteria? ;)

The differences among them are small compared to the overall badness. That is, on average all three are way more bad for you than the difference between the worst and the best of them. After all of the processing to make the oil, what you're left with is just oil and no (or very little) stuff is left over from the beginning. You take the beans/seeds/whatever and press the hell out of them, heat them, add some solvents, do lots of other stuff and you are left with poly-unsaturated oils. In fact, you probably can't even tell where they came from when you're done with it.

Corn and soybean oil have a ton of omega 6, way more than canola, which I think makes them worse. I suppose soy oil has some vitamin K1 and more omega 3's than corn, so if I had to guess I would rank them like this:

1. Canola (least worst)
2. Soybean (almost the worst)
3. Corn (worst)

http://www.marksdailyapple.com/healthy-oils/#axzz1uaTsxOWL

Likely that the industrial oils in restaurants are all rancid, honestly. And likely that they're all some sort of combination of cheap industrial oils. Sometimes what is labeled "canola oil" will actually contain soybean and other vegetable oils. "Vegetable oil" can be a combination of any kind of corn, canola, soy, and other oils. I know that when I have gone awhile without eating anything processed or restaurant-prepared, the next restaurant meal can cause a major gut ache, even if it doesn't contain gluten or additional corn or soy products (i.e. stir-fried veggies and meat... assuming it's cooked in some sort of industrial oil).

From what I know (not much) about hormones in soy along with the MUFA and PUFA levels and the omega 6 to 3 ratios, I'd think canola is the best option and soybean oil the worst... but then again, it's probably all rancid.

It is the difference between filtered and unfiltered cigarettes. Both are bad, filtered will kill you slower. Canola is the filtered cigarette. Soy and corn are the unfiltered. Canola has an inverted n6/3 ratio and is a processed food. Corn and soy have more anti-nutrients. If you are sick after some restaurant eating, it is most likely a sensitivity to one of these oils. I would guess soybean oil, but everyone is different.

Soy would be GMO too. I think it is the worst of the 3.

I would avoid all the oils you listed. That aside are you sensitive to MSG (MonoSodium Glutamate)? If so you need to ask if its used to preserve the salads and as flavor enhancers in the foods they prepare. If so you don't want to eat their unless you can live with the concequences afterwards. And if you are sensitive the bathroom is where you find yourself afterwards or with a gut ache to say the least.

I am going to say canola is the worst with soy a close second and then corn. The corn would be GMO though...

I use olive oil for most of my cooking. But for occasional frying corn oil has the highest smoke point and the least odor when frying. Canola oil has a bad smell when frying so I think it's the worst of the three.