my thoughts,
Wood:
Ups:Cheaper, Easier to Diy and to add a "wrap" of plywood or other things etc. Also the most easiest to find.
Downs: less underneath space, heavier.
Overall: Best option for simple freshwater setups or DingIY. only need to brush on some clear estapol to keep it water tight
Steel:
Ups:lighter, more underneath space ideal for "High-Tek" reef setups where space is needed for light controllers large sumps and skimmers, chillers phos,cal,kalk, sul and other reactors etc.
Downs: not the easiest DIY unless you have acess to equipment and know how to use it. more expensive. need to be powder coated which can get expensive.
Overall: the best option for setups which need alot of equipment.