Don't forget to factor in court surface and conditions. If you eliminate that as a factor I'd pick Murray...but on a medium/slow hardcourt played in the evening/at night (colder conditions would reduce the effects of Murray's slice), I think I'd favour Djokovic who seems to thrive in night matches, although slow conditions would also make Murray's defense more difficult to penetrate. In the three matches Murray won against Djokovic, it was either on a medium/fast hardcourt (Toronto '08), or in hot conditions (Miami '09), or both
(Cincinnati '08), so we haven't really seen the two of them play against each other under the conditions that would be present on the night of the AO final. I believe it's a significant factor - just think the 2010 WTF final, where the low-bouncing properties of the O2 arena court and the indoor conditions facilitated a Federer victory.
In terms of form both seem to be equally good so far in this tournament, although neither have been severely tested - Almagro and Melzer were both bad match-ups and played relatively poorly. The Djokovic-Berdych QF clash tomorrow will be telling.