Quote Originally Posted by Tavrobel View Post
Technically, he's more than one level less awesome, because Paras is part Grass, so it gets a defensive bonus against Water Gun and Bubblebeam. Butterfree has no such protection.
Plus Paras has (weak) offensive Bug attacks (actually just one at LV 20) and Starmie is a Psychic pokémon. But Butterfree Level 16 itself is stronger than Paras Level 17.