Generally, you should write for PEOPLE not the computer.
The "for(i = 0; i < 5; i++)" form makes it very clear that the valid range is "0 through 4" and nothing else.
And as other people said, this form make sure that funny code in the loop is much less likely to cause an infinite loop. And as other people have said, use the form that reflects what you mean.
Note that "less than" is the idiom commonly used in c (which means more programmers will expect that). That's another reason to prefer the "for(i = 0; i < 5; i++)" form.
