If bitcoin exchanges can be "scammed" why is bitcoin better?
Because you and I are not exchanges and Bitcoin is Peer to Peer. Exchanges are irrelevant to the question whether Bitcoin is "better".

Before you start, make sure to read all the introductory material on www.bitcoin.org so you know what you're doing and are choosing the right wallet and exchange.

Some exchanges are scams. Some are not, but may go out of business at any time, just like any company. Hopefully the ones linked above are at least not scams.

Use a reputable exchange (or another method, like localbitcoins) to buy Bitcoins and immediately withdraw them to your own local wallet. Don't leave Bitcoins on an exchange or web wallet any longer than required.

I've never heard of BitNake, but just the name screams scam. Stay away.