My experience is that there are effectively three "editions" as far as modern edition wars go. There's 4E, there's 3E/3.5E/Pathfinder, and there's TSR-era D&D. While 1E, 2E, 2E Skills and Powers, OD&D, and BD&D all have their adherents, they mostly get along with one another nowadays (back when 2E was the hot new thing I'm sure it was a different story).
At this point, anything made by TSR falls into the "old school gaming" category. 3E and 4E both represent radical overhauls, not just of the rules, but of the philosophy behind those rules. By comparison, the differences between 1E and 2E fade into insignificance. Even 1E versus OD&D doesn't seem like that enormous a gap; the rulesets are drastically different but they were built by the same people, with the same mindset.
1E seems to be the leader in the TSR coalition, with a smaller contingent of OD&D fighters. 2E is almost completely overshadowed by 1E for some reason. BD&D is not quite as completely overshadowed by OD&D. Meanwhile, the 3E faction appears to be roughly evenly split between 3.5E and Pathfinder, with a handful of 3.0 diehards.
As for which edition inspires the most heat? 4E, no question. It's the current edition, so pretty much all edition wars are in the context of 4E's present dominance. There's plenty of fodder for edition wars between 3E and TSR, but those guns mostly fell silent when 4E was announced.