Egg whites or protein powder?

They both have their place. I get bad gas from some PP. Especially concentrates.

But I've also gotten them from over consumption of EW's too.

My shakes (thanks to the advice from guys on this board) are pretty broad-based, so no one ingredient predominates. I have been using whole milk, natural peanut butter, bananas, raw eggwhites, protein powder (Optimum Nutrition Serious Mass) and cottage cheese...no gas, good results.

Anytime you use food then it is always better for you.

Use both. Find a protein powder that doesn't bother your gut. Try a high quality hydrolyzed isolate. Those are usually bullet proof. Use liquid egg whites as the liquid for mixing it in. U can even throw in a few raw whole eggs, if you're not worried about food borne illnesses; personally I'm not. The whole eggs add good quality fats and make it creamier. U can't taste them, and once their mixed in the shake tastes better anyway.

The research shows that multiple types of protein together actually make the optimal shake. U could even add some powdered beef protein to it. The more different sources of protein in your shake, the better.