The answer is: it doesn't matter.
You will not see any difference in performance in either, unless you really try hard to make code to see the difference, and what really matters is the readability of your code (and this is where you'll save time and and money in the future), so use whichever one is more understandable.
In your case, i'll suggest the While
approach ...
I'll also suggest reading this article by Eric Lippert: How Bad Is Good Enough?, just in case you're not sold on the readability vs. silly optimizations :)