I`m curious to see how much memory (if any) using the sprintf saves, instead of doing several serial.prints.
One Serial.print() or a dozen Serial.print()s take the same amount of code space. The code is only copied in once.
Using sprintf() in addition will increase the code size, since another function needs to be linked in.
It will not decrease the time needed to output serial data, either.
The only advantage to using sprintf() is for formatting, which is hardly an advantage, since you are only dealing with char arrays.