I would hazard a guess that the amount of oxidized cholesterol in the tissues of grain and soy fed would be higher because of the higher amounts of omega 6, but don't know of a study.
The bigger issue that would affect you is the mycotoxins from the food source that get stored in the animal fat, which have a greater effect on your VLDL and LDL than the cholesterol itself in the meat.
I have a video at http://www.bulletproofexec.com/bulletproof-video-get-stable-energy-perform-better-by-avoiding-these/ where I go through the effects (cancer and cardiovascular) of mycotoxins at low levels in the diet.
By the way, for my friend Angry Jeff who frequents Paleo Hacks and always has something constructive to say, this is another of the reasons the Bulletproof Diet is different from Paleo - my recommendations control for mycotoxins and other toxins, whereas Paleo diets often allow mold-contaminated foods, along with their xenoestrogens. Improperly stored or processed grass-fed meat is simply bad for you. I eat almost no xenoestrogens or other toxins, which is one reason I can eat 4500 calories/day for long periods without significant exercise while remaining muscular and lean. What you don't eat is as important as what you do eat.
