OkieG,
I have had both steel and wood gooseneck trailers. The steel trailer was 15' flat with a 5' dovetail,, tri-axle and weighed about 5,000lbs. The wood trailer is 34' flat with no dovetail, dual tandems, about 7,000lbs.
The steel surface is more slippery than the wood, especially when wet.
I replaced the wood floor, (all 34' of it, and it is 8' wide) with "rough cut" lumber from a local mill. My total cost including bolts to secure it down was about $250. I cut them up and put in myself.
You can also add D-rings or other hooks to wood trailers too!
Depending on where your braces are at and how thick the steel material is,, steel will "bow".
Both surfaces have there pros and cons. I sold my steel trailer and kept the wooden one,, no regrets.
RedDog