This isn't a new question, and it's not one that both sides are going to agree on in the near future, if ever. Me, I'm all for science. But I'm not happy with animal rights being violated either. (For the record, I eat meat but don't think I'm a hypocrite for being against fur.)
Still, how can you make a decision?
Take for example this story. Scientists are apparently trying to figure out how some animals grow back body parts, so that the same technique can be used with humans. If they figure this out, there's no end to the benefits for medicine. 50,000 people lose a body part to amputation every year in the US alone. If scientists can make the technology work, all these people could have their fingers, hands, arms, and legs back in a matter of weeks or months.
So that's a good thing, right?
Not for the animals that have the regenerative abilities.
Take for example Salamanders. These animals can apparently grow back an arm if it gets severed. How often must scientists make cuts in a salamander's body to find out what chemicals, enzymes or glands are involved in the regrowth? How often does someone cut off a Salamander's body part to observe what happens?
Scientists have got far enough to grow extra arms on salamanders. Does the salamander feel any pain when it is cut, or when it has an extra arm coming out of where there should only be a simple rib? Unless the researchers are extremely careful with anesthetics, there's probably a lot of pain involved for the poor creature. Does the salamander know about the value of the sacrifice it is making? Surely not.
A hundred years from now, the number of people who will have benefited from regenerative technologies will probably be close to one billion. There will still be those who demand that researchers stop testing revolutionary medicine on animals. They will still be right. But so will the scientists.