c compilation - gcc vs visual c

hello:

I recently compiled a numerically intensive c project under cygwin gcc
3.4.4 and microsoft visual c. The platform is intel T2400 1.83 ghz
dual core lap top.

the numerical stuff is both floating point and integer intensive

The gcc optimized (-O3) vs non optimized improved the performance 30 %

visual c optimized (standard , check 'release; under visual c 2005)
vs non optimized ('build') was a whopping 8x performance gain

but the most surprising thing was visual c optimized was 2x
performance over gcc optimized.

is anybody else seeing the same thing. if this is true microsoft c
compiler is in a different league altogether

i was not successful so far compiling under mingw. will it make dent ?
2x is hard to overcome