You can stack consoles givong the same bonus, but the percentage return goes down (Note the percentage return is calculated on the BASE damage values of the weapon).
If you stack consoles giving two different bonuses, then that can be more efficient.
Cannon console (+11 to all cannon weapons)
Disruptor console (+15 to all disruptor weapons)
This would buff your disruptor cannon damage by 26% (11 + 15), THEN your captains training in those catagories is added to the calculation.
I 'think' thats it, but I'm probably wrong. Not sure again how much the decrease is on stacked consoles with the same buff (was an old thread from long ago).
I don't know if the percentage is right, but the concept is. The two consoles he is talking about would stack for full effect of each, however if you had 2 Tac consoles with +15 disruptor then the second one would give a diminishing return. At least iirc that is how it works, but I could also be wrong.
Mouse over your canons and look at the DPS each one does.
Replace disruptor console with cannon console.
Look at canon DPS again. Determine what the net gain/loss is. Then you'll know which one is better.
I often have mixxed damage types, some phasers, some disruptors, even had 4 types at once a one point while leveling simply because I couldn't get anything to drop that matched up. Depending on the level of the item, how many you have equipped, etc, sometimes specific consoles outperform generic ones or vice versa.
One thing I will say though is that 2 tactical consoles of the same quality and level, specific damage types ALWAYS have higher values than generics.
Your best bet is to stick with one type of damage so you can buff all of it at once.
I personally find phasers to be the best damage type in the game so far that i've played with, and i've used tetryon and polaron weapons as well.
The proc on phasers, with the chance to instantly drop all shields on the target is just so amazing, so much more benefit than the other little procs here and there.