Trapinch
But that's only if you're going to evolve it in to Flygon. If not, stick with Dugtrio.
At present Trapinch is sufficient, but very quickly you'll realise its speed and bulk isn't good enough to actually help you out. Dugtrio is much faster and more likely to help you win a battle. However, should you choose to invest time to evolve your Trapinch, you will find that it's significantly stronger (although still slower). And you get a Dragon type Pokemon which are quite strong, but the trade off is how long you have to work to get
them. Fortunately you get Vibrava in just 2 more levels, but honestly even as a Vibrava it's still a little underwhelming.
But, all said and done, for an in-game team, if the rest of your team is overleveled, you needn't worry and keep Trapinch around without evolving. It's obviously better to have cute Pokemon on your team than grinding it to a not-so-cute version if you're not having fun.