You're right to think that they convey broadly the same meaning. Which one you choose will depend on your focus. In a reference book you would see 'Pumas are large animals' or even 'The puma is a large animal' - where 'The puma' is used generically.
If you were telling a story about walking through a jungle, and suddenly seeing a puma, you might say 'I turned a corner and was suddenly confronted by this huge puma. Now a puma is a large animal, and I was pretty scared. Luckily, though, he was intent on <whatever> etc etc...'