Battering Blast
Pros:
- 3rd-level spell
- Ranged touch attacks, usually fairly reliable.
- Force damage, which few enemies resist.
- Targets specific enemies, so you don't need to worry about allies in the AoE.
- Can also knock enemies prone if the bull rush succeeds.
Cons:
- Close range.
- Doesn't bypass SR.
- You only get additional targets at levels 10, 15, and 20.
Other:
- It's not clear whether the save would be Ref or Will. There's a Ref save if the bull rush is successful, but it doesn't affect the amount of damage.