Uh
What
They've all got the same base stat total. All of them. All three of them reach a grand total of 500 bst. Notice how Pinsir and Heracross swap base stat difference? 15, 25, 15, 25. The pattern repeats, and two of their stats are identical. Scyther and Pinsir don't share this. At all. Both of them also have a dramatically different move pool; while Pinsir and Heracross almost have the same move pool (Heracross having what you could consider and upgraded version of the two of them). There move pool, of course, doesn't make as much a difference as their stats do, it's just another similarity between them.
What
They've all got the same base stat total. All of them. All three of them reach a grand total of 500 bst. Notice how Pinsir and Heracross swap base stat difference? 15, 25, 15, 25. The pattern repeats, and two of their stats are identical. Scyther and Pinsir don't share this. At all. Both of them also have a dramatically different move pool; while Pinsir and Heracross almost have the same move pool (Heracross having what you could consider and upgraded version of the two of them). There move pool, of course, doesn't make as much a difference as their stats do, it's just another similarity between them.