On the other hand, the snake park is overwhelming, one of the best I have ever seen throught the country. It has huge variety of species of snakes and crocodiles, with origin from far distant lands of myanmar, Sri Lanka, etc. If you have to choose just one, opt for the snake park, your money will get it's worth.
At one point of time, you might start feeling uncomfortable watching too many huge snakes and crocodiles, just with a safety of glass in between. I would definitely recommend to visit the snake park, though you may skip the so called national park.