The value of both revolvers depending on condition is not much difference. The model 10-5 are modern short action revolvers. M&P before 1947 are long action revolvers. Some people believe the long action revolvers had the smoothest double action and single action trigger that S&W ever made. If you can find a nice 4th change for about $350 I would jump on it. Later you can always by a 10-5 because they are more common.

Good luck,
Howard