Essentially boosting trumps all because of time investment.

Once you hit 15 you can be 23 in 1 hour from stockades runs.
Another hour you are 35 from SM runs
Another hour you are 45 from SM runs and a run or two of stratholme
Another hour to hour and a half you are 58 doing LBRS runs
Another hour you are 65 from ramparts and a few sethekk runs
Another hour you are 70 from sethekk + UK
Another hour you are 74 from nexus (2 runs) + DTK + 2 runs of Gundrak
Another hour you are 78 from another gundrak run + AoA + 2-3 HoL runs
Another 30 mins and you are 80

Total time: 12 hours from level 1 with BoAs

If you quest... You can see that it takes you 2 hours to do 1-15 or so. After that your travel time increases due to quest hubs being everywhere and doesn't actually get any faster till flying in outland.

You can have 15-20 mins or more of every hour be travel time between quest npcs, quests and the next zone due to raf exp requiring you to move zones very rapidly.