Here is my 2 cents:
1. That Intel complier 2 times faster than MSVC compiler is too impressive to be true. If the observation/measurement is vaild, then this could be a good indication that the program is not well written or not well optimized (complier independent opt).
2. Intel compiler is fast and beats MS one inalmost allof the cases. 15% speedup coming from a compiler for free (yes free of asm coding) is stillquite good.
From the options used "/QaxSSSE3 /QxSSSE3", it will run the code path with SSSE3 optimization on a system with Intel processor with SSSE3 or higher. The default optimization is /arch:SSE2, so on other systems, it will run the code path optimized using SSE2.
Please see this article for some detail info about the processor targeting options.