Mining a specific cryptocurrency (i.e. Zec) can be more profitable than mining another currency, i.e Bitcoin. Thus a key question for miners is: what is a good cryptocurrency to mine currently. The cryptocurrency profitability depends on a lot of factors, such as equipment cost, your hardware hash rate, power consumption, and the current Bitcoin price (or, for altcoin mining, the current price of that altcoin relative to Bitcoin).
There are various online mining profitability calculators. Most of them compare cryptocurrency (altcoin) mining to Bitcoin mining using a statistical calculation based on the hash rate value which does not account for difficulty and exchange rate fluctuations, stale/reject/orphan rates, a pool's efficiency, and pool fees. So your individual profitability may vary. Use at your own risk:
The profitability of mining an altcoin/cryptocurrency, other than Bitcoin, can be also related to its current price relative to Bitcoin. Thus, you might want to track changes in cryptocurrency exchange rates for the past 24 hours, week and month: