Correction, assassin armor pierce only gives incorrect amounts at earlier percentages, probably due to rounding if I had to guess. At 100% it goes through all armor, assassin is absolutely better. But as for orbital, I’ve had it do an amazing job at activating vampire ice and static. Lava, however, is an on land effect, meaning that it only activates with regular attacks, burst, multicast, etc. This is almost absolutely because of orbital, as otherwise it’d instantly form an impenetrable barrier of lava. The reason I focus so much on late game, though, is because I don’t tend to struggle with early/mid game, so long as I don’t get really unlucky with dice, but by all means that’s where orbital shines and armor shred sucks.
Stacking bullet speed is very valuable in the mid game though, as with high bullet speed, orbitals can make you effectively invincible with enough damage. So long as you target large slimes (or red caterpillars when necessary) before they reach your orbs, nothing can really get through it. Also bullet speed is just useful, as it causes you to lose less bullets when you switch targets and helps with red caterpillars which are otherwise too fast.