In my opinion, both of those pokemon supports a deck in a different way. Claydol is good against any Disruption cards like Absol SW, TGW & TGM. You can use Claydol to counter that. As for Porygon 2, it will help you in your setup by playing another Supporter during your turn but beware, Porygon 2 can be an easy target for Gardevoir LV X's Bring Down due to its 70 HP. So, it's up to you. Maybe you can try play testing both & see which one works best in your deck...