Both are valid, but immersion leads to spectacle like this much more readily:
Baptism is a solemn, sacred occasion not a party as they seem to be taking it. Pouring the water seems to reduce the chance of it turning into a party game. (And why shouldn’t it surprise this come out of Los Angeles?)
Hat Tip: The Cafeteria Is Closed

That’s just goofy. You’re not supposed to baptize infants by immersion.
“That’s just goofy. You’re not supposed to baptize infants by immersion.”
Jesus, is that You?