I'd have to agree with TC there Warlock.. the 51 is a very capable plane at low alts and slow speeds, if you can control the plane. Most who can't do BnZ in it, which gives the pony a bad name as a "runner"plane because majority of those who fly it, can't fly it like some of those who were previously mentioned.
What Dedalos said is correct as well as far as the spits, F4s, etc beating the pony. Same thing can be said about the F4 and K4. But those who are good in them, can control their plane at any speed/alt. Which makes not so much the plane itself deadly, but rather the pilots knowledge and skill level.