I prefer to buy ready made house from a trusted real estate agent, because it will saves me a lot of time and headache, I don't have to worry about the building engineer buying sub standard equipment or over charging me, or none of that.
If you're a business minded individual you'll understand that time is money, and there are better ways to utilize the time rather than worrying about worrying about building a house, but if you opt for buying a house, you'll pay up once for all and all you need to do is to just move in, no stress.