Olive Oil: Different Kinds - Which is Best?

We use olive oil for virtually all cooking.  My wife insists on extra virgin.  I've tasted them all:  extra virgin, extra light, just plain olive oil, etc.  They all taste the same to me.  Are there any health reasons for using a particular grade and not the others?  Do other people find there are taste differences?  

[caregiver222]

The extra-virgin is unquestionably the best tasting. Head and shoulders above the rest. People have difference in their abilities to differentiate in tastes. Do not purchase large quantities of any grade olive oil because it tends to deteriorate and become rancid once the bottle is opened.

[bbxx]

The more (virgin) it is the better for you. I cant remember all the details, but I looked it up before. One bit of interesting info I found out back in my  olive oil research days, was that if the oil is not virgin, the company is legally allowed to add a certain amount of  other oil to mix in with the olive, like corn oil. Not right, but allowed. I only buy virgin olive oil, and caretaker is right---it goes rancid. It can however but used for a lantern light if its rancid.

[margypops]

I use the extra virgin I find it does have a stronger more olivey taste but I like it, its very expensive now.