I'm proud to say i passed the Advanced Airway practical exams last night in my Basic class. =] I definitely prefer the Miller in Adults and Children, Macintosh in infants. This is only from experience on dummies though, I'm sure once i get in the field my opinion may change.
The straight blade is the recommended blade for infants utilizing a size 00 - 1 blade to lift or compress the base of the tongue. A #1 Macintosh could be useful for a slightly bigger infant or one with an anomaly.
A Macintosh blade may work on a manikin, but a real infant will be very different. I have yet to find an infant intubation head that is even close to a real baby. The better quality adult intubation heads do give you some idea of the procedure but several live intubations will need to be done to adequately experience the procedure and the different complexities of the human body.
Again, I choose the appropriate blade based on the assessment of their airway.