Mathematically the profitability of any cryptocurrency can be calculated by using the formula that determines the average earnings of the miner depending on its computing power and coin that it mines:
Earnings (1 MH⁄s per day) = (Block reward) × 20.1165676117) / (Complexity ) × (Rate,Bid)
This formula is valid for any of the mining algorithms. The specific fork is determined only by the size of the reward for the block and by the current complexity of its production.
You need also to consider that the same hardware shows different Hashrate (computational power) depending on the used algorithm. Table below presents the background data about the performance of AMD graphics cards, depending on the algorithm that used by developers of different cryptocurrencies.
Comparative computing power of the ATI GPU for different algorithms relative to the Scrypt algorithm
The data from the table can be used to analyze and compare the performance of processors for different algorithms.
The block reward as a rule changes rarely and remains constant for a long period of time. But the rate on the exchange and the current complexity can change quite rapidly during the day both the larger and the smaller side
Modern software for producing cryptocurrencies can monitor the change of complexity of the process for each coin and its price in real time, and switch to the mining of the most favorable fork from the list.