Only need to do one STF per day to get your fix of marks (and some surplus, at least initially) - so I'd certainly do that.
If you find the time and drive to also do Romulan dailies: go ahead - a few of those will net you enough marks, too.
Overall it's only an hour of game-time or so to get marks to keep both lines running for two days.

Ultimately you'll likely need more Omega marks than Romulan ones, altho this isn't always true; and Omega marks are easier to get as well.