- College infielders in general seem to be a solid way to go, as many college infielders get moved to different positions (often the outfield) during their minor league careers. The biggest surprise there has to be first basemen, however, as those guys don't shift positions as often as other players; apparently they're just extremely reliable hitting prospects.
- Among high school hitters, catchers and third basemen were the only reliable choices. Shortstops weren't terrible, so one could consider those players as well. This makes sense, as the best high school athletes are often put into those key positions. Other positions, particularly on the right side of the infield, were disasters.
- If you want to take a pitcher, college pitchers--particularly left-handers--continued to be the most reliable picks. High school righties were also reasonably good choices as far as pitchers go. College right-handers, however, were surprisingly poor choices.
- At least one reason for this is probably that right-handed pitchers often have to be very talented to succeed in the major leagues. Since the best righty talent in the country usually gets gobbled up out of high school these days (high signing bonuses, etc), fewer of those players go on to college. This makes the talent level of right-handed college pitchers rather poor.
- In contrast, left-handers often can make it and perform well in The Show with less overall talent due to their advantages vs. lefty batters. It's the 'ole "crafty lefthander" scenario: there are almost twice as many left-handed pitchers (~26-27%) as there are left-handers among hitters or in the general male population (~14%), indicating a lower overall talent threshold (assuming being left-handed is not "talent") for making it to the majors among southpaws. Predicting which lefty pitchers will be "clever" enough pitchers out of high school to succeed in the majors is apparently a very tough exercise as those players have a lot to learn yet about pitching. College pitchers tend to be more polished and closer to being big-league ready, making it easier to pick the smart and crafty-types from that talent pool.
Rany's articles do a great job of investigating specific success and failure stories for each position, so if you're interested, I highly encourage you to head over there and read through his articles in detail. There is a subscription cost, but you can test-drive their site on a month to month basis for only $5. If you like what you see--and I'll vouch that it's the best baseball info you'll find on the web--you can then subscribe for $40/yr.
Update: This information may be particularly interesting for those participating in the Minor League Ball mock draft on Sunday, June 4.