I'm curious, what is the weight difference between the two yard boxes? A 20 lb difference versus a 200 lb difference could possibly change some of the previous opinions.
While I don't disagree with the posts suggesting the heavier one, I will add that if the lighter one will do the job that you are trying to do (I'm pretty sure that it'll do as good as the heavier one for moving/smoothing gravel) then I'd be tempted to save the $200 ...IF... that is going to be the primary job for the yard box (>95% of the usage?).
However, if there was a possibility that you'd want to scrape up soil or do other yard box work on more than very rare occasions, then I'd CONSIDER following all of the "go for the heavier box" suggestions previously mentioned. Problem is, sometimes it is hard to predict how often you will end up using that new piece of equipment...
Bottom line: The heavier box won't make much difference on some jobs and will be a much better tool for other jobs. I'd say that the lighter box will perform nearly any task that is better suited for the heavier box, it just may take longer to accomplish compared to the heavier box. Consider the frequency that you'd be performing these "other" jobs and decide if that is worth an extra $200. Obviously, for most people that have responded so far, the answer is "Yes, it is worth it".
Kelvin