1. Welcome to the site 2. All questions are welcome. 3. I own both a direct impingement and a gas piston ar308 (larue obr 20" and a 14.5"Pws mk214) To answer the question which is better is like asking why a Chevy not a Ford. Arguments can be made for both, so I say just buy American! As far as I have heard, there is no definite reason one is better than the other, although there are many claims. Now for the answer to the best question you asked. Building one will allow you to get exactly what you want. Yes, it will cost more. No,its not that difficult. You will end up with exactly what you picture you're rifle to be. Pro's to building are you don't have to get it all at once, you get exactly what you want, buy once cry once. Con's are it's more expensive usually because you most likely won't cheap out, you will buy better parts off the shelf costing more, and may go through a period of waiting for parts. I think its "Cheaper" to get the dpms at first, but if you start changing things out, say the stock, trigger, handguard, now you are into build price range. Choice is always yours, I think you'll here many opinions on this, and would say think of what you want in the end and go for it.