I observed a huge performance difference between Ant 1.7.1 and the actual 1.9.3 using win7 and Eclipse 4.3.2.

Here is my example test project:

<project name="doit" >
  <echo>ant.version=${ant.version}</echo>

  <exec executable="cmd" dir="c:\">
    <arg value="/c" />
    <arg value="test.bat" />
  </exec>
</project>

test.bat just produces a lot of output (10'000 lines with 1'000 chars each) and containts the following:
@for /L %%i IN (1 1 10000) do @echo 1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890

In this case, the eclipse console speeds things up for 1.7.1!

Here are the times for my doit-example on my machine:

        win console    eclipse console
1.7.1    42 seconds          1 second
1.9.2    43 seconds         38 seconds
1.9.3    43 seconds         37 seconds

And console output in eclipse is not limited!

There is some discussion about this issue in Bug 54128 which led to this new bug.