Usually you can look at their attack stats in game, and the higher one is generally the one to go with in most cases.Thank you guys! Much appreciated.
How do you tell if a Pokémon is a physical or special attacker?
If you're still unsure, look at their movepool, if they have better physical attacks they are usually a physical attacker and vice versa. That said, movepool can be the thing that turns what looks like a physical attacker into a special attacker (and vice versa). Look at Tapu Koko for example, it's physical attack is higher than it's special attack, but it is most commonly run as a special attacker because of its movepool.
Some Pokemon are mixed, and have very similar physical and special attack stats, but even then you usually want to lean one way or the other, most Pokemon don't have the stats to pull off good mixed sets (Salamence, a 600 BST monster has some successful mixed sets purely because it has such high stats).