Completely different games.
In stud-8, you can tell which of your opponents are likely playing for a hi, which for a lo, and which for both.
In O8, you have to assume that every one of your opponents is not only drawing for both, but drawing for the nuts in both. You simply cannot play for a second-best low or a merely decent hi.
That's not even getting into the vast differences between a stud game and a community-board game.