Nicehash is good at the beginning, when you are learning how to mine, if you are lazy and don't want to deal with exchanges and if you want to only accumulate Bitcoin in a simple way.
You are selling your hashrate to another person in been paid in BTC
The minimun amount of BTC to withdraw is 0.0005 BTC at the moment, the fee for withdraw is variable, for now is 0.000005 BTC but can increase if network is overloaded.
The fee for miners is 2%
With Nicehash you can do more, you can change BTC for a coin you want, for example Litecoin, and withdraw Litecoin instead of BTC, so you have a lot of possibilites.
Here you can see the comparison between Nicehash and/or mining directly:
https://whattomine.com/coinsThe alternative I suggest you is keep mining with Nicehash and learn about mining directly, you can mine ETH in a pool like Ethermine and receive in ETH, this way is more profitable than Nicehash most of time