Simply put, the big one has far more bubble output- about 10,000 BPM (bubbles per minute) than the small one- about 4000 BPM. That said, the smaller one is not really that small if you're not comparing. 

But, it doesn't have lights like the big one and is not rechargeable. First video below shows the Big model followed by the small one. 

Here's a video of the base model shot in our warehouse.