The two expansions come with identical Team Upgrades for the original teams.

I assume we are meant to just use one of them?

Wakrob

yup, your assumption is correct yeah the reason why they send those with both expansions is so you can play each expansion singly and have the extra upgrade for each team. other wise you would have to by both expansions in order to have a full game with six upgrades per team, and that wouldn't be too fun for beginners who wants to play the stadium expansions but don't have the money for both expansions.