I'm lazy so rather than typing a longwinded reply myself I'll just quote Squire's excellent post on an earlier thread:
"The whole business with the Brewster in US service came down to a single dogfight on June 4th 1942 at Midway. The 15 Buffalo and 7 Wildcats were launched late vs an IJN strike of 108 a/c. They were faced with 4-1 odds as well as this was the first combat of almost all the USMC pilots in the war. They fought as well as could be expected, and actually impressed the Japanese. It would have made no difference if all the fighters were F4Fs in that fight, none whatsovever.
The Brewster in Dutch and RAF/RAAF service in the East Indies is a circumstance where the air force is faced with the land ans sea forces being defeated and forced to withdraw, it was not the fault of the Brewster that they were in such poor circumstances. The presence of F4Fs or P-40s or Hurricanes would not have prevented that campaign from being the disaster it was. Nor would they have altered the Singapore campaign.
Its ironic that the P-40 at Pearl Harbor and the Phillipines is not blamed for the Allied defeats there, or the F4F blamed for the fall of Wake island, but somehow it seems many want to blame the poor Brewster for all the ills of the Allied forces in those early weeks and months of the Pacific war in other places. Its more to do with our human need for symbols. We dont like defeats, and anything associated with a deafeat gets all the harsh mythology that goes with it, and the opposite for the good times, where victories come, we over glamorize anything associated with winning, the P-51, the Spitfire, the Hellcat, ect. Its the same for ships, tanks, guns, and anything else we associate with a particular battle.
So take what they say about it with a grain of salt, and understand the context of the very difficult circumstances it fought in before beleiving all the over hyped smears and half truths. Was it a great fighter? no, but it wasn't as bad as many make it out to be through the crud colored glasses of Allied retreat in those early days of the war.
As for Finnish service, the Finns had the benefit of being able to operate it for almost three long years from airfields that were not over run, and were able to fight a long war of attirition over home territory against poorer Sovier pilots and tactics in many cases. I take nothing away from their accomplishments, they did a splendid job, but the circumstances were very different."
I totally agree with Squire. This is partly the reason why there are still discussions where Brewster is sometimes referred as the worst fighter of WWII. Considering that things like the I-153, I-16, Gloster Gladiator, CR.42 fought in WWII the whole question is absurd. But the myth lives on when a big war whinning nation happened to get the snot beat out of them in one aireal combat the plane it self had to be complete junk...
Regarding the Brewster vs. Zero-5,
Given equal pilots, the reach of the .50 cals and the vastly better rollrate are a real problem to the Zeke driver but the significant climb rate advantage that the Zero enjoys can really be poison for the Brewster. Hi Yo-Yos and spiral climb can be used to defeat the Brewster once it starts gaining Zero on the turn.