I believe many Braves fans found it surprising that Brandon Beachy beat out Mike Minor for this season's 5th starter spot in the Atlanta rotation, but both have seen considerable action this season anyway.
In the interest of comparing the two's situations, there are a lot of things to consider. However, I'm not going to attempt to find which is better or worse. They will both be Braves for a long time, barring a trade.
First, their major league performance thus far.
Brandon Beachy has started 23 games, earning himself a 3.31 FIP (87 FIP-) during his tenure with the big-league ballclub. He's struck out 9.95 batters per nine (26.5 K%) while walking 2.71 per nine (7.2 BB%). Batters have a .298 BABIP, fairly run-of-the-mill. Meanwhile, Minor has a sterling 3.01 FIP (78 FIP-), striking out 8.88 per nine IP (22.1 K%) while walking 2.80 BB/9 (7.0 BB%). Minor's opposing BABIP is .357, which suggests he's been a bit unlucky on balls in play and accounts for some of the differences in ERA.
Based upon these past performances, Beachy projects a 3.30 xFIP (85 FIP-), a 3.60 tERA and 3.01 SIERRA. Minor projects a 3.49 xFIP (89 xFIP-) with a 3.79 tERA and 3.46 SIERRA. So, while Minor's actual performance has earned him a better FIP, he does not project quite so well as Beachy, probably because of his low HR/FB that does not project in xFIP as well a 24.7% LD rate that isn't well-liked by tERA and SIERRA.
The final consideration to be made, as with all young players, is service time. A full season is considered 172 days, but partial seasons still count. This actually plays out fairly big in the comparison.
Although Beachy had just 14 days of service time before 2011, he's been with the big-league club all year (or on the DL, which counts against service time). So, unless he's miraculously sent down to finish the year, he's going to be at 1 year, 14 days going into 2012. As such, he projects as a free agent after the 2016 season. This assumes, of course, that he's not demoted for any length of time, as his minuscule 14 days of extra service time could easily be swallowed up by such a move.
Minor entered the year with 58 days of service time, but actually projects to have less than a full season by year's end. According to my calculations, he should end up with no more than 163 days of service even if he stays with the Atlanta squad for the rest of this year. As such, if he never sees the minor leagues again, he will be a free agent after 2017, one year later than Beachy. That said, he's almost a lock for Super 2 status (if it is kept in the CBA, which is not certain), which means both will hit arbitration in the same offseason.
Both players' eligibility for the ROY award will end after this season. I don't think either figure to be significant candidates for the award, though Beachy could potentially jump into the spotlight with an incredibly impressive September. Right now, he's a darkhorse candidate at best.
So, when comparing the two, here are my conclusions:
1) Both are really good, with every single advanced metric coming in below 4.00. That's pretty astounding and bodes incredibly well for both of their futures.
2) The Braves will likely get an extra year of Minor, but at a cost. However, baseball has become a game of team control as much as on-field performance. The majority of the teams in the league don't have two players that meet the level of performance described in my first conclusion, let alone the amount of service time remaining with each. This is a huge advantage for the Braves.
So, sit back, relax and enjoy both of these guys, as they project to put up 3-4 fWAR per season well into the future.