That does not backup your claim about single table read vs multiple table reads. I can't see your claim being substantiated. As for your test, time does not say me anything. What does the profiler say ??

Sorry, my mistake, I was wrong about that, they're both hitting the invoice table twice. Jury will disregard. (I still prefer the CTE approach for readability, though I realize that can be a subjective thing).

I'll get back to you tomorrow with what the profiler says.