Saber Score and Sim ROI both come from contest simulations and they are both an ROI percentage for your lineup — the difference is which contest sim that ROI is coming from.
Sim ROI uses contest sims specifically based on the contests that show up in your entries file, or custom contest sims that you’ve created yourself. These contest sims use the real sizes, payout structures, and projected fields of each contest you’re playing, recognizing the precise differences in what makes a lineup good in a large field MME contest and a small field single entry contest.
Saber Score, by contrast, uses a simpler contest sim. It’s still using a GPP payout structure and field lineups that resemble what your opponents are likely to play, but they’re not based around the parameters of the exact contests you’re playing.
Because of this, Sim ROI is going to be a more accurate and precise measure of the quality of each lineup in your pool for your specific contests, but Saber Score is still a strong alternative that will give you an idea of the general quality of a lineup.
If you’re on the SaberSim Ultimate plan and have access to Sim ROI, you should use it over Saber Score because of that increased accuracy, but our backtesting shows that both Saber Score and Sim ROI deliver profitable lineups into your contests.