strategies for Multiple pairs or multiple strategies on a pair

if you guys want to make more than 1 strategy, which option you guys would do? or which one you think is better.
 
A) strategies for Multiple pairs  (example : 1 EA for EURUSD, 1 EA for GBPUSD etc)
 
B ) multiple strategies on a pair(example : 2+ EA for EURUSD)
 
C) others you may have

A combination of A and B makes sense to me.. my aim is to create a heap of UNCORRELATED strategies that have good returns and very minimal draw down. Stagnation doesn’t worry me as much (but I try to reduce it) because no strategy will make money ALL the time, so if they are holding their own in the bad times that’s good enough for me. 

I personally use approach A – different strategies for different pairs

 

But I have a friend who is running a portfolio of strategies on just one symbol – so both approaches could work.

As nolube mentions, the key term here is correlation. 

Here is a definition of the Correlation Coefficient:

A measure that determines the degree to which two variable’s movements are associated.

i.e

http://www.investopedia.com/terms/c/correlationcoefficient.asp

If two Forex pairs have inverse Correlation Coefficients e.g. EUR/USD and USD/CHF

or the same then it wouldn’t make much sense to have differing strategies for each of these pairs.

 

Whereas the pairs EUR/USD and AUD/USD would have differing Correlation Coefficients

and so should have differing strategies, in my opinion.

 

A good article on the subject is here:

Using Currency Correlations To Your Advantage
http://www.investopedia.com/articles/forex/05/051905.asp

Another important consideration is a pairs Standard Deviation or

measure of its historical volatility.

Even if two pairs do correlate their Standard Deviation may be radically

different and thus require completely differing trading strategies.

 

Standard Deviation

http://www.investopedia.com/terms/s/standarddeviation.asp

In my opinion making one strategy that work well on different pairs would have sense. It would be a proof of the concept used in this strategy. Even if EURUSD have his own historic volatility, it wouldn’t be the same in a near of far future. So, if a strategy work well on many different pairs, it has the power of “ruling” the market, in any condition.

 

Of course, it wouldn’t have to be perfect, but with a good profitability.