Moved into new house a few months ago. I got a sloping back yard with an existing retaining wall that looks "do-it-yourself". It needs to be redone. The wall is at the property line in the backyard and faces a side of the next house. There is zero curb appeal and even those in the backyard won't see the wall. Given that fact, I am leaning towards the cheaper timber, but some contractors warn against it. Some say no problem, they can last 20 years easy with no fail. The cost difference is about $2000. Advice?