They serve completely different purposes. Supernova is good for area denial whereas Valiance is better for interruption and direct damage. Quite frankly, they can complement each other very well.
If I got to choose only one of the two I'd pick Valiance because Supernova doesn't stand well on its own feet. You'll need a complementary gun like a Blaster or an Antigua. Valiance, on the other hand, stands very well on its own feet and doesn't need any complementary weapons.
They serve completely different purposes. Supernova is good for area denial whereas Valiance is better for interruption and direct damage. Quite frankly, they can complement each other very well.
If I got to choose only one of the two I'd pick Valiance because Supernova doesn't stand well on its own feet. You'll need a complementary gun like a Blaster or an Antigua. Valiance, on the other hand, stands very well on its own feet and doesn't need any complementary weapons.