There are hundreds of different kinds of aloe plants. I believe there is only one that is considered to be medicinal Aloe Vera. Do you trust your nursery person? Many of them are quite knowledgeable and others are just there for the paycheck.
The other problem with aloe vera is that it must be used or ingested almost immediately as it begins to break down shortly after harvesting.
I have heard there is a product on the market that is patent pending. The company has found a way to stablilize and standardize aloe vera. I will try to find out about it if you are interested.
Have fun with your herbs!