Sabathius42 said:
Maximized Empowered Scorching Ray (same level spell as maximized orb) yields 108 points (216 on criticals, 0 for misses). Thus the orb spells are underdamaged compared to an SRD-only option.
If one were only to look at damage and your math were correct, your point would be well taken. The metamagicked Scorching Ray does do 3 more average damage than the metamagicked Orb with no other factors considered (93 versus 90).
However, these are 8th level spells.
By the time the casters are throwing 8th level spells, there are more defenses against the Scorching Ray which do not affect the Orbs as greatly. For example:
Energy Resistance 5: Scorching Ray 78, Orb 85
Energy Resistance 10: Scorching Ray 63, Orb 80
Energy Resistance 15: Scorching Ray 48, Orb 75
Energy Resistance 20: Scorching Ray 33, Orb 70
Energy Resistance 30: Scorching Ray 3, Orb 60
Also note that Fire Resistance is found on more creatures in the Monster Manual than any other type of resistance. One could research different Energy type Scorching Rays, but as a rule of thumb, those are typically not available in many campaigns.
Also, Spell Resistance. The Orb blows through SR completely. Scorching Ray does not.
Plus, the Orb still has the save for a secondary effect.
Scorching Ray can be stopped by both versions of Globe of Invulnerability whereas the Orb can only be stopped by the 6th level version (presumably).
Overall, these particular metamagic versions of Scorching Ray and Orb still have an edge of Orb over Scorching Ray. In an average campaign, the metamagicked Orb will average a lot more damage at 17th+ level in the long run.