Very difficult one. I think the difference is too small between the two.
Both have six titles resulting in a tie.
Consistency:
Next best results Fed: One final and 7 SFs
Next best results Djokovic: 3 QF and two 4R
Federer has: 11 consecutive SF (2004-2014) and 14/15 SF (2004-2018) vs. 2 consecutive QFs for Djokovic
Fed wins easily in terms of consistency. Not even up for debate.
Dominance:
Djokovic has: 5/6 titles and three consecutive titles, better winning percentage overall at 88.4%
Federer has: 3/4 titles and two consecutive titles in two far removed periods (2006-2007 and 2017-2018), won once without dropping a set in 2007, more wins overall with 94, more top 10 wins overall with 21
Much closer call than deciding regarding consistency. Djokovic wins in terms of dominance IMO though Federer could stear it his way if he wins AO 2019.
The H2H is too circumstantial for me, baby Djokovic vs. peak Fed and old Fed vs. Peak Djokovic. Age gap too large, not too relevant imo. 2008 Fed was not old but he wasn't playing well. For me, the result of 2008 is as relevant as the result of 2007.
Their opponents in finals:
Fed dealt with Safin (AO champion), Nadal (AO champion), Murray (5 times finalist), Bhagdatis, Gonzalez (won against Nadal) and Cilic.
Djokovic dealt with Nadal, Murray and Tsonga (humiliated Nadal).
Slight edge to Djokovic because Federer had Bhagdatis. Zoning Gonzales = zoning Tsonga and both men beat Nadal to advance to their finals. Futhermore, both men had Nadal and Murray. Additionally, Federer had Safin (very good at the AO, 1 title and 2 additional finals) and Cilic. Bhagdatis gives the slightest of slight edges to Djokovic regarding difficulty in opponents met in the final.
I guess a Djokovic fan will favour Djokovic and Federer fans have more than enough ground to give the edge to Federer. For me, there is no clear cut answer though Djokovic has enough time to end the debate by winning 7. Federer won't win the AO anymore I think (hope I'm wrong). Federer still has 3 titles on rebound ace and 3 titles on plexicushion (nothing against Djokovic just something to behold on Federer's part).
For me at this moment, it's a tie because I value both Djokovic's dominance and Federer's consistency equally.