Being ahead sounds important to me if you wanna quest your way up. I can see quite some bottleneck quests where people fight over spawns. If you are 1 level ahead, I figure you end up with quests/zones that are easier to complete.
I'll go with the full quest log from northrend/stormpeaks into cata. Then chain pulling rnadom wotlk hc dungeons till 81. And then move into cata.
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