Evaluating two different Algorithms, which one will scale better?
You are not looking for asymptotic behaviour, but for actual runtime for rather large n; you determine how large. 

You can either analyse both algorithms, and estimate what their run times will be, or much easier, you can measure it. You have to be very careful if you do this with an optimising compiler, because they tend to throw away operations if they can prove they are not actually used. But done carefully, this will give you the actual numbers.

Draw some graph showing the runtime depending on N. And be aware that different processors or different compilers can produce rather different results. Also be aware that if the time "jumps" for certain sizes of n, lets say 50n nanoseconds if n &lt; 10,000, 100n nanoseconds if n &lt; 1,000,000 and 200n nanoseconds if n > 1,000,000 then your time may be depending on memory access, and you can often improve time significantly be re-arranging operations.