Physically, they have a lot in common. They were born less than six months apart. Davis is listed as three inches taller and 20 pounds heavier than Havens. They both bat lefty, but Havens throws righty. They are both from the United States.
Ike Davis was selected 18th overall in the 2008 amateur entry draft, after a junior year at Arizona State where he hit .385/.457/.742 with 16 home runs. He walked almost as much as he struck out in his final year, and steadily improved for each of the three years he was at Arizona State. Davis is a gamer - he posted a 2.25 ERA as a pitcher and could comfortably play the outfield as well as first base.
Reese Havens was selected 22nd overall in the same draft, after a junior year at South Carolina where he hit .369/.486/.645 with 18 home runs. He walked more than he struck out his final year, and steadily improved for each of the three years he was at South Carolina. Havens is a gamer - on draft day, Baseball Prospectus called him "a monster makeup kid who could move quickly" and "the Mets 2B of the future."
Both Havens and Davis had extremely shaky debuts for the Mets. I got a chance to watch them both as Brooklyn Cyclones, and their statistics backed up what I saw. Davis looked like a power hitter who could not hit the ball deep anymore. Havens looked better.
Davis struggled to a .256/.326/.326 finish in 215 at bats, with a 23-43 bb-k ratio. Havens was marginally better, batting .247/.340/.471 with an 11-27 bb-k ratio in only 85 at bats.
Most Mets prospect enthusiasts knew well enough not to put any stock into that short cameo. The adjustment to the pros is difficult - and in my limited experience with Brooklyn, the fact that it is sea level, and by the water, and usually very humid, works a major detriment to hitters. Pitchers tend to fare well at Brooklyn and balls which appear to be crushed die before the warning track.
Next season was going to be the big one for both prospects.
Real World - St Lucie:
In 2009, Reese Havens posted a very respectable .247/.361/.422 line over 97 games, with 55 walks to 73 strikeouts. Ike Davis, however, was the one that shone. In 59 games at St. Lucie, Davis hit .288/.376/.476. Then, after a promotion to Binghamton, he did even better -- batting a phenomenal .309/.386/.565 in 55 games.
Now is the part why I tell you Havens is better than Davis. Havens was extremely unlucky last season, while Ike Davis, on the other hand, was lucky.
Reese Havens had only a .277 BABIP last season - an unusually low number. BABIP stands for batting average on balls in play. Ike Davis, in his time in St. Lucie, posted a .352 BABIP -- an 80 point gap.
Of course, there are lots of reasons why two players BABIP's may be dissimilar. However, both of these guys played in the same league and park, and had the same system taking care of their statistics. The most obvious remaining reason for the difference is - of course - that maybe Ike Davis was simply hitting the ball better. Not every batted ball is created equal. Although there has been much discussion academically about whether or not a batter can control their BABIP, I fall very much into the camp that they can.
In this case, however, the disparity is not explained. Though they both hit around .700 on line drives (as one would expect on the hardest hit balls) their splits on ground balls and fly balls were very different.
Fly Balls: Havens, .213 v. Davis .258
Ground Balls: Havens, .214 v. Davis .314
Once again, not every batted ball is the same -- but with things broken down to this degree of specificity, one might be inclined to believe that this is just luck, or statistical noise. I do. I believe that Ike Davis is a better hitter than Reese Havens, and that he may, over his career, carry a better BABIP than Havens. However, that is not where this analysis ends.
No matter how they do at the plate next year, one thing is undoubtedly going to be true: Ike Davis is going to play first base, and Reese Havens is going to play second base. That is the great equalizer.
It is common knowledge that a good-hitting second baseman is infinitely harder to find than a good-hitting first baseman. The same goes for all difficult defensive positions in comparison to first basemen. That is why Chase Utley was worth 7.6 wins over replacement last season while Prince Fielder was worth only 6.8. That is why Troy Tulowitzki was worth 5.4 wins over replacement and Mark Teixiera was worth only 5.1.
For the record, a second baseman is approximately one win more valuable than a first baseman provided everything else is equal. People much smarter than me have determined that a win is valued at roughly $4.5 million according to what free agents have been paid over the last decade.
The conclusion is that if Havens can hit nearly as well as Davis, or at least within shouting distance, he will be a more valuable commodity to the Mets because of the positions they play.
For kicks, minorleaguesplits.com provides a "luck" adjusted form of statistics. By clicking a button, you can see, as an example, what a player's statistics in a given season would have looked like, provided they recieved average luck. Here are the lines for Havens and Davis in St. Lucie, last season, given average luck:
It is important to note that Davis then continued on to hit even BETTER in Double-A ... but that is not the point of this exercise. The point is to show that Davis and Havens are in the same orbit when it comes to their performance at the plate, and nobody knows it.
I would put Havens a hair ahead of Davis on any prospect ranking I made - but I can understand why I'd be in the minority. The point is that they belong in the same breath - not with Davis as an up and coming stud and Havens as an afterthought.
 To continue playing my game of "He Reminds Me Of" ... here are these guys.
Reese Havens = Bobby Crosby, Michael Young, Troy Tulowitzki
Ike Davis = Adam LaRoche, Lyle Overbay, Travis Lee with power
 For the record, without thinking about it too hard, I think my top ten would look like this:
1. Fernando Martinez
2. Jenrry Mejia
3. Jon Niese - Guy tears a hamstring and we forget all about him? He dominated AAA as a 22 year old. He did the same in AA at 21. He held his own in the majors this year. I think Niese is the real deal and I'm ready to anoint him as "arrived"
4. Wilmer Flores
5. Reese Havens
6. Ike Davis
7. Josh Thole - A personal favorite, as a catcher I think he'll be hugely valuable. He'd rank higher if not for the concerns about his defense.
8. Dillon Gee - Quietly excellent last year. 7.8 k's per 9 in AAA last year as a 23 year old, that is what I like to see. Reminds me of one of the many good-but-unspectacular Twins pitchers... like a Kevin Slowey type.
9. Jeurys Familia
10. Jefry Marte