In recent comments, I stated I'd rather have Braylon Edwards than Anthony Gonzalez (and that it was a no brainer) and also Michael Crabtree over a steadier option like Steve Breaston. While one can argue quite persuasively that the expected return in total fantasy points on Gonzalez and Edwards is close - and also that Breaston's is likely quite a bit higher than Crabtree's - especially in what's likely to be a run-heavy 49ers offense, those arguments miss a central point: that there's a bigger difference from second place and first, than second and last.
If we were talking about the stock market where every dollar counts equally, I think you'd be wise to pick the investments purely on the basis of expected return. If you swing for the fences too often, you'll get a five bagger occasionally, but you'll lose most of your investment on many others. The net might not be pretty, and for many, that kind of risk is unacceptable. Whether you are in the 80th percentile among investors or the 20th is all the difference to most people.
But in fantasy sports, the utility curve is far different. Winning is the goal, and the difference between finishing in the 20th and 80th percentile in your league is usually not that important. (There are some exceptions in leagues which pay good money a few places in and also for those that closely track average lifetime finish). But for the most part, it's about winning titles. In that case, each player must be evaluated differently - he needs a "chance that this pick wins me my league" factor.
Crabtree could score 10 touchdowns - he's a prototypical red-zone target on a team that lacks that. He could also do nothing. But Breaston is right now the Cards' third receiver, and while he's a better bet for 800-plus yards, he's not going to get targets in the red zone with Larry Fitzgerald and Anquan Boldin on the team. He has a lower "win your league factor" in my opinion.
Now, keep in mind that almost every player has |STAR|some|STAR| potential to break out, even ones we don't see coming. That DeAngelo Williams would score 20 TDs (and literally win hundreds of thousands of people their leagues), despite having Jonathan Stewart in the backfield with him was almost inconceivable. Same with Thomas Jones' monster year (check out how horrible his 2007 stats were), so one should realize that we're not always right in our upside projections, either.
But we do our best based on skill set, role, team context, etc., and try to get a handle on who the game changers are. We're not dealing in certainties - just possibilities. Every round after the second, you draft the player with the most plausible path to superstardom (given even a roughly comparable expected return).
The other reason this is a sound strategy (besides the steep climb in the second to first utility curve) is that unlike a stock, a player's floor is capped. If you buy a stock at 100, its value can go down to zero. But if you buy a player for a certain price, his value can only go down to replacement level. So even though Crabtree could be a nonfactor this year (and Breaston if healthy almost certainly won't), their downsides are not all that different because Breaston's is 750 yards and three TDs, hardly above replacement level in most leagues.
You should be less aggressive in the first two rounds because every player has the chance to be very good at that stage, and the replacement level floor is cold comfort in that case. Otherwise, swing for the fences.