The disadvantage of Wet/Dry is nitrate retaining, you can take care of that if you have something to denitrify at the laterr stage of your filtration, or cleaning your balls frequently and properly.
The advantange of Wet/Dry is aeration. It is VERY efficient way of supplying oxygen to your system without micro bubbles. Most reefers will spend extra money on water flow like powerhead to supplement the missing aeration. With water flow method, make sure you have it breaking the water surface so that gas exchange can occur easier.
So if you already own one, it will not hurt to add it to the early stage of your filtration(provided that you have a DSB, Macro Aglae somewhere in the system to denitrify the nitrate), in a mix environment but there is no need to buy a new one though since you are most likely to have a very BIG pump and all the goodies like tunze and such in your tank.