When Logic 8 came out I was frustrated that it was no new features compared to Logic 7 only a new GUI, so I bought myself a PC and Sonar 7.
I tried to learn Sonar 7 and made a few productions with it before I turned back to OS X and Logic, due to the horrible Windows OS.
The fact is that my mixes with Sonar 7 sound different than my Logic mixes.
I can´t say it is better or worse and don´t know reasons why, It may be different included plugins but I use a lot of UAD plugins too...
So, for me, the choice of DAW will affect the sound.
Mac Pro 6 core, 24 GB RAM, 285GTX, AVID HD I/O, UAD-2 Duo Satellite, PT HD3 PCIe ,Control 24, PT HD 10.2.0, 10.6.8