A man should not use a soy protein powder as soy protein powder is an estrogenic. Soy also has a very poor amino acid profile.
The best protein supplement is a pure whey isolate. It has the highest bioavailability and best amino acid profile out of all the different protein supplements available. All protein powders are not created equal. You really need to be a smart consumer in today's market and do your research. Look at the ingredient list and supplements fact panel on every supplement before buying it.
For a whey protein - you want to see nothing but that in the ingredients list. Whey protein, natural flavours, a natural calorie free sweetener like stevia and then maybe some salt, soy lechitin and cocoa powder. There are a lot of good products on the market. I personally use isolation from n2bm.com. A good whey isolate should be pretty much fat and carb free. Isolation has 26g protein, 1g carb, 0g fat per 30g scoop.