... apparently I need to reiterate my other point.
Sin deals with magic, and heavily relies on it [despite its monstrous size] whereas to deal any severe damage Vegnagun apparently needs to rely on his main cannon. Sin requires little time to charge any magic attack [Giga-Graviton excluded, though I still think it takes less time than Vegnagun's cannon to power up] whereas Vegnagun has... very little support fire from his main attack. Yes his tail could hurt the party, yes the main body hit a bit - but against Sin? Seriously? By the time Vegnagun whips out his cannon Sin could potentially destroy every ounce of the machina.
Sin deals with magic, and heavily relies on it [despite its monstrous size] whereas to deal any severe damage Vegnagun apparently needs to rely on his main cannon. Sin requires little time to charge any magic attack [Giga-Graviton excluded, though I still think it takes less time than Vegnagun's cannon to power up] whereas Vegnagun has... very little support fire from his main attack. Yes his tail could hurt the party, yes the main body hit a bit - but against Sin? Seriously? By the time Vegnagun whips out his cannon Sin could potentially destroy every ounce of the machina.