If designed properly, wood is not a concern. Strut may be easier to work with, but likely a bit higher $$ due to the price of the steel and hardware.
If I were you, I'd check out some of the rigs in the picture thread and see if any of the wooden stands appeal to you. Maybe price some lumber vs strut material and see what you think.
If you are hooked on brewing and plan to do it for years, it may be worthwhile to build a stand you really want now, even if it costs a few dollars more.
If price is really a concern, look for a metal scrapyard in your area. I usually find something useful every time I go down to ours. It's probalby about time now that winter is over...