Spiny vs Maine lobster. What's the difference?

They are two different animals. Maine lobster generally has much more meat on it than a spiny lobster, which is more like a langoustine, only bigger.

Maine lobster is way tastier. Maine ocean water ranges from cold to frigid. It is only sold fresh and alive, or cooked and then sold as frozen lobster, which is an abomination, IMHO.
I'm from Maine, so I may not be 100% objective. Come visit. We have lots of lobster.

Actually California spiny lobster lives in fairly cold water. The season for them is fairly short, beginning in September and they have to be harvested by hand. For that reason they are about 3 times as expensive as Maine lobster. The meat tastes better if only because they are fresher. You can by live Maine lobster just about anywhere in the country but they don't eat in captivity and tend to shrink inside their carapace. It's true that spiny lobsters don't have large pincer claws.

Spiny is a warm water lobster with no front claws, also known as rock lobster. Maine lobster is a cold water lobster with large front claws. Some people say that the difference in the tail meat is that Maine is firmer and sweeter.