If you can swing it without excess financial pain, as far as I'm concerned buy the good one right off the bat. Buy once, cry once. Otherwise you buy the cheap one now, and then some time later spend more $$ on the good one, thus kind of 'wasting' the money you initially spent on the cheaper one.
Obviously this doesn't apply if you can't afford the good one right away (thus my financial pain comment above); in that case the cheaper one is better than not having one at all. That being said, I can't think of a time when I've regretted buying the good tool over the cheap one if I was able to afford it.
-Pat