I have not written anything that would qualify for the contest, so I can't speak to it directly.
But as for which is more valuable.... Either one would further your career, obviously. The real difference, I would think, is that the contest only matters if you win. And like any competition, when someone wins, everyone else loses. So if there are three fabulous books, the judges will still have to choose just one of them as the final winner. But agents aren't restricted by contest rules. So all three of those fabulous books could be picked up by an agent. In that sense, then, I think your chances are better of landing an agent than of winning a contest.
On the other hand, winning the contest makes it easier to find an agent. So I don't think there's anything to lose from entering the contest.
This is a very slow profession anyway. It took me six months to get an agent to request to see my full manuscript. It may take her another two or three months to decide whether or not to make me an offer. If she passes, I have other agents I'll be querying--who knows how many more months. And then there are still the submissions to editors, which could take even longer. So if you are hoping to get a quick answer.... Well, it does happen. But waiting until October is not really that long.