There's no question that Dwight Howard has been a far superior NBA player to Al Horford over the past three seasons. So far this season, Horford has closed the gap significantly despite his team's predilection for giving priority to 30-year-old offensive-minded guards over young, well-rounded post players.
Dwight Howard has a significant advantage over Horford as a scorer because Howard has been almost as efficient as Horford despite being a far larger part of Orlando's offense than Horford is of the Atlanta offense.
Scoring doesn't tell the whole story, as Horford is far more likely than Howard to earn an assist and far less likely to turn the ball over
26 of Horford's 86 assists have resulted in three-point baskets. 14 of Howard's 22 assists have resulted in three-point baskets.
Thus, the 4.2 point (per 36 minutes) scoring advantage Howard enjoys over Horford is more than negated by the extra 4.8 points (per 36 minutes) Horford's passing creates for his teammates and Horford's efficiency advantage only increases when the two extra turnovers Howard commits every 36 minutes are accounted for.
To be remotely comparable to Howard, Horford has to out-produce him with the ball in his hands because of all that Howard does to get the ball. Horford is a very good rebounder (13th in the league in defensive rebound rate, 17th in the league in total rebound rate this season) he's just not nearly as good a rebounder as Howard.
Howard makes more defensive plays than Horford, as well:
Defensive plays do not tell the whole defensive story and both players play a key role in their team's defensive systems. Neither the Hawks nor the Magic have had a major drop-off when Horford or Howard have been off the court this season: the Hawks give up 1.3 more points per 100 possessions with Horford on the bench, the Magic give up half-a-point more per 100 possessions with Howard on the court so far this season but Howard certainly deserves credit for Orlando's general defensive excellence whereas Horford, it must be acknowledged, does not appear capable of elevating his team much above the league's defensive average.
So, yeah, as we all knew, Dwight Howard is a better basketball player than Al Horford. The larger point here is to illustrate that Al Horford (season-to-date) can be reasonably compared to Howard, that Horford is plenty good enough to be the two-way focus of his team's attack, should not be hidden from the likes of Semih Erden, and should not be the fourth offensive option on any team.
Every day the Atlanta Hawks persist in resisting, on the court, to play through Horford and, in the front office, to build the team around him is a partially wasted day.
*Especially if "you" are a member of the Atlanta Hawks organization.