I'm trying to figure out my dream shop. Steel or wood, but I don't see wood at 12 foot walls and 60 x 70, but we will see. Don't want to hijack your post so will at some point start a post to discuss.
Wood would be more expensive at those dimensions, especially today. Steel trusses can easily handle 60 foot span while lumber would require some "engineering" for that size of span. The 12 foot walls aren't a problem for either wood or metal but lumber would be expensive at today's prices.
For a shop that size you should hire an architect/engineer to put together a set of plans and then get it bid out by a couple of contractors. I had an architect help me with my shop design and he saved me from a bunch of mistakes.
