Our first 4 drives went end on downs, fumble, punt, fumble, so that is true. Sims led us to three TDs, but was also responsible for two turnovers that BC got 14 points off of, so net he earned us 7 points. Graham got 4 drives and scored 1 touchdown, with no turnovers, also earning us 7 points.
If you want to be pedantic Graham only got us 6 points not 7 (although I don't think it would be fair to make that distinction).
But more precisely, saying that each turnover cost 7 points is assuming a lot. One that they would score definitely and that the defense takes no responsibility for those points when they could have held them to a FG. I don't really mind not considering this though. The more important thing though is that saying it costed us 14 assumes that had we punted instead, that we wouldn't have given up points. With our defense that isn't a fair assumption to make, and so it's likely that even without the TOs we'd have given up points on the resulting drive so the turnovers, so they overall differential in expected points given up from that drive resulting in a TO vs a punt isn't 7 points. Ironically the best argument for it being that much is that Sims was likely to drive us down to score, but that's a zero sum game for pretty obvious reasons.
But the most practical reason is that saying they played the same doesn't really address who played closer to what we need from our QB. With our current team, both defense, OL, and WR/TE groups, we need a QB who can make plays and consistently drive us down the field. Sims is just better at that. Graham doesn't turn the ball over as much, but he doesn't move the ball as much either. Basically imagine this scenario where two cases have 5 scores with the following outcomes.
case 1: 5,6,5,4,6 for an average of 5.2
Case 2: 2, 9,7,7,6 for an average of 6.2.
The averages aren't that far apart, but case 2 has he clear advantage of if you can replace one outcome, it greatly changes the average. Replacing the lowest score with a 9 would yield 6.2 for case 1, and 7.6 for case 2. That is basically where we are at now. Sims is better in ppd than Graham despite the big mistakes, and it would take less improvement to make a bigger impact. It's easier to fix a small number of high impact mistakes vs a large number of low impact mistakes.