In a big bowl, combine the popcorn and 1 1/4 cups each of the peanut butter chips and chocolate chips. Toss to distribute evenly.
In a medium saucepan over low heat, melt the butter, sugar, corn syrup and marshmallows, stirring constantly to keep the mixture from burning.
When the sugar mixture boils, pour it over the popcorn mixture and stir to evenly coat, then quickly but gently form balls in the size you like. Place them in small bowls or the wells of a muffin tin that have been lightly coated with cooking spray so they hold their shape as they cool. Pretend you're making snowballs but don't pack them too hard.
In two separate small saucepans over low heat, melt the remaining 1/2 cup each peanut butter chips and milk chocolate chips (or microwave in two small bowls) and drizzle the two over the cooled popcorn balls.