Yes there is a difference between avandia and glucophage
basically, glucophage tells your liver to decrease it's glucose output. Avandia makes the insulin receptors in your body more sensitive to insulin, making your cells absorb the glucose from your blood.
Which one is more effective depends on why you have diabetes. Some people have excessive sugar output from their liver, others have an insensitivity to insulin. And others have insufficient insulin output from their pancreas. Most have diabetes due to a combination of these factors.
BTW, glucophage has a potentially fatal side effect if taken in large doses. It's called lactic acidosis. If you find you're unable to sleep (I'm talking about being able to sleep for 20- 30 minutes at a time maximum), or symptoms of restless leg syndrome appear, stop taking it immediately.
This happened to me when taking avandamet about 2 years ago. turns out the company making it had a recall due to improper quality control resulting in wildly varying doses of glucophage. The FDA shut them down and confiscated their stock until they could demonstrate proper dosage control.
be careful with this stuff.