The thing about concrete ties (timbers) used in switches is that each one is made for a specific position. If you need to replace one or more you must have the specific pieces to do it. In a switch using wood timbers, any timber can be used in any position that it is long enough for. Spikes and/or screw lags can be placed wherever they are needed. Need an 11' but don't have any? Throw in a 12' or a 14' or a 16'. If you like, cut off the extra length with a chainsaw and you're golden. Concrete ties give a much louder ride than wood, at least in M/W equipment. Concrete ties and timbers are also much heavier than their wood counterparts. While wood, even 22' timbers, can be replaced using hand tools, concrete requires the use of machinery, which requires at least foul time, more likely a line 4 track OOS. Concrete ties will hold the gauge until they are pretty much destroyed. Wood ties will gradually lose their ability to hold the gauge, getting worse as time passes. There are some wood ties which are remarkably resistant to age and weather. I have seen ties from the 1930s which are still doing their job as well as any that were installed last week.