Nice hash is good as you get paid directly into BTC without having to exchange yourself, which incurs fees.
The instant exchange also allows for you to pick up price rises before the price drops again, this happened to a lot of people with ZEC slow start - the price had dropped before you could get the coins to an exchange to sell them.
Most pools charge 1% anyway so I don't see a further 2 percent making me poor.
Your example with the ZEC slow start may be a good use for nicehash, but it almost all other cases it is better to mine them at a 1% pool and exchange them yourself.
The decision probably comes down to how many rigs you are running and how soon you need the cash from your mining. I could see a strategy of allocating say 20% of your hash rate to a place like nicehash so you can consistently be paid in BTC which you then cash out to USD to pay your electric bill, but the rest would be better traded at your discretion to get the best price.
Of course if you just have one or two rigs the convenience of nicehash might outweigh the extra profit motivation.
