Would having a dragon type be better than having a grass? Well honesty i've never had a grass or dragon types on my past teams.
Honestly as you probably saw I have an Altaria on my Platinum team and she really isn't that great. Like it's decent, but you could do better. So if you were thinking of a dragon poke you might wanna look into some other ones.
I just started playing Pokémon Diamond for the very first time. I'm trying to catch and train as many Pokémon as possible so I can switch up my team often.
I'll just stick with Tropius since he can use Fly. Almost all the winged Dragons can't learn Fly until their final evolutions, so they would kind of be useless on my team majority of the game.