I don't like any of the dedicated tank-buster planes. To me, their guns aren't noticeably more effective than those of other planes. Against light armor, any plane's guns will kill, and tanks can be disabled by pretty much by any gun as well. In terms of killing tanks, the tank-buster guns don't seem to have much chance of scoring a direct kill, although they do seem to have a slightly higher chance of disabling the tank than regular guns. As has been said, disabling tanks often gets you kills when the nme bail out. However, the tank-buster planes are deathtraps in air-to-air, so you're often dead yourself before the nme bails.
Bottom line IMHO: the tank-buster planes sacrifice too much performance and ordnance for too small a gain in guns effectiveness vs. GVs.
Therefore, the best anti-tank planes IMHO are those that carry lots of bombs and/or rockets. It's nice to have some of both (ex: F6F, P38), or lots of bombs (ex: Me110) and still retain decent air-to-air performance once they're gone.
Of course, the best thing for killing tanks is a Tiger.