Foldovers are wrap style bodysuits with two flaps across the chest and four-snap button closures to keep it closed. Foldovers are perfect for infants less than 6M's old. Babies tend to freak when something goes over their heads and faces (try and and you'll see the startle). Not everyone gets bothered by it though!
Pullovers are just like any other shirt. Slide them over and instantly fully clothed. Pullovers are great for all ages, but especially as your baby gets older and the squirming gets real...the last thing you'll want to deal with are four extra buttons!