Uruk-hai are likely a bit stronger, both in general and in this particular match-up: the higher Fight allows them to win more combats, while the S/D means they wound the Rohirrim on 5s (shields) or 4s (archers), compared to 6s (shields) and 5s (others). On the other hand, having a few more guys is a great benefit and the extra Might on Eomer will allow him to dictate the game a bit more, picking advantageous fights and throwing a few more spears. (Will be a few days before I can check on Éomer's profile, but I don't believe he has changed much over the various editions. You can check the curent profile in LonelyKnight's armybuilder
viewtopic.php?f=42&t=22221).
Overall, these seem like decent starting forces: diverse weaponry and stats and a thematic confrontation to boot.
2x2 is fine for a dozen models a side, although for shooting to have an impact, the forces best start near the board edges. Make sure the board is nicely filled with scenery, it will look better (a major draw for new players) and hamper Isengard's shooting especially (since the crossbows can't move and fire), evening the odds a bit. Make sure both forces are painted (again, a good first impression really helps) and maybe create a small narrative for the game. For the very first game, it may be easier to leave the heroes out (focus on the profiles, line of sight: the basic rules), although things like heroic actions do greaty enhance the game. If all goes well, continue the story with e.g. cavalry reinforcements to teach those rules, or a confrontation with Gandalf or Treebeard when the evil forces flee into Fangorn (introducing magic and monsters, although the latter are only really different from the Hobbit rules onwards).