[NTLUG:Discuss] Internet connection speed tests - XP vs Linux

[terry]

I've done a number of speed tests (testing Internet connection [bandwidth]),
using 2 PCs; MS Windows XP system and a Linux system, (same speed test on
each).  It appears that 4 out of 5 times, the Linux system usually gets
faster speed test results.  I'm using the latest Firefox browser on both
systems and going to the same bandwidth test site on each and running them
one right after the other.
(Both systems are fully updated - latest patches etc.)
I did about 4 or 5 tests a few days ago and while I did not calculate the
exact percentages, I did see fairly consistent faster speeds from the Linux
system.

This time, I calculated and Linux was faster on all but two tests;
Here are results [percentages]:
Test#                download (%)               upload(%)
  1                       6    [faster]                   50[faster]
  2                       32  [faster]                   55[faster]
  3                       11 [slower]                   55 [faster]
  4                       21 [faster]                    0  [about the same]
  5                       15 [faster]                    62 [slower]
Does anyone have any explanation for this?
Has anyone else done speed test comparisons like these?

Is it possible that Linux has a more efficient TCP stack?
   Or....?