Research shows that formula fed and breastfed babies tend to get the same amount of sleep overall each day — it's just the timing that's different between the two groups. (bluesmartmia.com)
Hubby's went off at 6:30 a.m., so we were getting about the same amount of sleep. (heligirl.com)
Neither seems to impact what happens throughout the night (she's up and in our bed around midnight for the rest of the night) but she does sleep later if she goes to bed later, so she gets the same amount of sleep. (sarahockwell-smith.com)