Richard - take note, I'm voting for an English player over an Aussie.
TBH, I'm sorely tempted to vote for an Australian player over an English one. Not really sure, however.
In any case, I obviously never said "every Australian will vote for every Australian player ahead of any other" (I know sideshowtim will, but he's an exception). And of course you know that.
Trueman has more than fair claim on being England's best seam-bowler ever; Davidson has more than fair claim on having no Australian seam-bowler better than him. The way Davidson has always suffered, in my view, is the same way Jacques Kallis has - his natural reticence. Davidson was one of the most uncharismatic cricketers ever; Trueman one of the most.
The one thing that's always held Davidson back in my view is the fact that his career was a short one. He played well for only 32 Tests over little more than 4 years. He was 26 on debut, 29 by the time he became established in the side (previously he'd played just 12 Tests out of 24 and averaged 34) and retired aged just 33. This is much shorter than most of the best bowlers, and only his phenomenal record in that time (averaging 19.25) puts him in contention. Only very few have ever managed such a good average even over the relatively short period of 32 games.
Trueman, on the other hand, did almost all his best work in England and missed countless Tests for mundane reasons - ie, because he'd upset someone or other. However, this work was for the most part phenomenal, spanned a large number of years, and every single team he came accross - none of them managed to conquer him on home ground.
Perhaps purely for the fact he's a Yorkshireman, I'll have to vote Trueman.