Was this question really that hard to answer???
S.S.4 Gogeta has a 100X Big Bang Kamehameha attack
S.S.3 Gotenks has the Super Ghost Kamikaze Attack
Although the two kids are strong indeed, there fathers have way more power and experience. Although youth is a good thing to have on your side, it also will lead to hasty decisions instead of carefully thought out planning. I do give them credit, but in the end...I firmly believe that S.S.4 Gogeta will/would prevail.
Death is but a door, Time is just a window,...I'll be Back!!!!!