Exposures. Your baby will be at risk for more germ exposures against just one caregiver.
Not sure. The advantages of grandma vs. Daycare maybe more one on one attention, and less exposure to viral illnesses. The advantages of daycare maybe socialization, and, actually, exposure to viral illnesses. There is alot of eveidence that exposure to illneses leads to a healthier immune system, and less infecctions as a child ages. I feel this should always be a personal choice.
Perspective. Kids love grandma vs parents prefer daycare. Grandma difficult to have boundaries i'n all angles. But grandma cheaper materially but costly emotionally - you either way pay - how is your perspective.