Garrad put up 25 points against Ten earlier in the year. Pretty much every quarterback that has gone up against Tennessee has put up more than 15 points. So, it's pretty safe to assume you're looking at a guaranteed range of 15-25 for Garrad, which is pretty good. Garrad has had his off weeks for sure, but I don't think week 8 is going to be one of them.
While Ryan has potential to do as good as Garrad, he also has potential to do worse, especially against NO. If it were me, I go with the safe play and start Garrad.