Build with what you are comfortable working with,either wood or steel will build a fine cradle.While i prefer steel a few years ago a friend bought a 25ft full keel
sailboat which was in Seattle
sitting on Jackstands in a driveway between a house and a fence in the suburbs,we drove out from Minnesota
with a 3/4 ton diesel
pickup truck,a rented 10000 lb flatbed trailer and a bunch of tools,we got there,sized up the situation,made a run to home depot for lumber
etc and then erected a cradle under the hull
and then removed the stands and winched it onto the trailer with 2 come alongs,strapped it down and got a motel for a good nights sleep and were on our way home at first light and yes,the wood cradle worked just fine for a 1000 mile plus road trip.My point is if you are more comfortable working with wood and are not going to be using a commercial boat hauler go for it.