If you're trying to pick favourites, shouldn't you decide yourself instead of letting us pick?
Anyways, both of them are around equally good. The main problem here is not how they compare to each other, but how they compare to the rest of your team when they are obtained at such a low level. If it helps decide, you can look at their stats and what moves they learn on serebii or something.
If you still want a suggestion, I personally think omastar looks kinda stupid <_< --- THIS IS WHAT I HATE A BOUT EVREY WEBSITE!! THERES SO MUCH PEOPLE READING AND POSTING STUIPED STUFF