Your starter will not be appreciably stronger than other tems. Most are balanced out to be somewhat usable I'm the endgame, whether it be by stats, moveset, or ability. I would argue that some starters are just better than other due to their type being hard to find until mid game and useful early on. Also, tems that don't evolve will be way stronger in the early game, since they are somewhat balanced with tems that do evolve later on.
Don't be scared to experiment with different tems and see if some fit your playstyle better, because of that.
There are also occasionally hidden or hard to find areas that have a very small chance to find a tem that's only available there. These tem are usually pretty good, so you may want to spoil yourself if you want to catch them all.
Also, much like Pokemon's IVs, tem have stats that vary. However, these numbers are visible to you. If you know you want a tem on your team, it might be worth catching a few for better stats.
Finally, unlike in pokemon where creatures evolve at a set level, tems evolve after gaining a certain number of levels after capture.