While I agree with both, j and Hipkiss, that the second one is faster because you compare i against a value instead of doing the math on every iteration, imho, this is a fine example of micro-optimizations. Even if you make sure to write all your loops that way, the actual benefit is so small compared to all the care you have to put in there, that I'd say you shouldn't bother too seriously about it.
Write your program. Is it fast enough? If not (and only then), profile your code. What is your hot path, and what is the bottleneck in your hot path? More often than not, you can gain big speed-ups by optimizing your algorithm used in that very place.