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Main difference is the current transfer ratio (CTR), that is Ic/If @ some Vce. Sort of current gain. The 4N26 (20%) is higher than the 4n28 (10%), and the 4n33 is a darlington output for very high CTR (500%)- i.e. high gain, if you like. The higher the CTR, the lower the LED current required for a given output current. Don't let the output saturate, the performance will degrade.
In your application the substitution should be fine. You may have to fiddle with R1 to optimise it, depending on the input voltage you are using - probably 5V.
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