LFS promote the wetdry because they are easy money. The bioballs are a nitrate factory. That is their intended purpose in a
FW tank.
FW is what they were designed for, and they work well in that environment.
SW is a different animal.
However, the wetdry isn't a total loss. You can usually convert a wetdry into a refugium/sump without much of a hitch. Just leave the blueballsofdeath out of the sump and sub in some live sand and a nice macro algea. I personally like to have a thin layer of filter floss for some mechanical prefiltration in the trickle chamber, but some would argue even having that.
LS and
LR will provide all the chemical filtration you need. A good protein skimmer will take care of most partially disolved solids as well as keep your water in good general condition. Skimmers are basically a 'high tech' mechanical filter.
You mentioned a light hood. Normal output florescents will not cut it in a
SW tank. You need at least
VHO or
PC, and if you want some advanced corals or clams, you need
MH.
Some basic advice:
Plan a lot. Then plan some more. When you think you have a handle on it, go back and plan again. Get a good handle on what you want in your tank. Don't use the 'I'll just add the things I like as I go' method. You will run into a lot of problems.
Learn as much as you can about the hobby. Ask around a lot. Only take advice from
LFS that you know you can trust. Some are not as honest as they could be. Some are worth their weight in gold for the advice they dish out. You have to decide which is which.
Buy the best equipment you can(t) afford. High quality equipment lasts longer, and provides you with more consistant and better results overall. Skimping always costs more in the long run.
Take things slowly. The only things that happen fast in a
SW environment are disasters. It takes patients and planning to adequatly immitate an ocean. The old saying haste makes waste is big time true in this hobby. You will sacrifice hundreds ... yea thousands of dollars worth of livestock to the porcelein god if you rush into things too quickly.
Wish ya the best of luck. Keep us up to date on how you are progressing.