In the old days we used to scratch build RC model aircraft from plans, or basic kits using balsa, dope and tissue. Times have moved on and technology has changed, now modern high quality composite materials and plastics are used, kits are now mostly semi finished assembly jobs, ARFT, or more commonly RTF (ready to fly out of the box) like RTR railway models. Not as many folk are prepared build things anymore for a whole range of reasons. I guess materials such as brass and white metal are the equivalent of the balsa and tissue materials that dominated model aircraft construction decades ago. There is no right or wrong just what one is used to. But today one senses most consumers want high quality RTR straight out of the box, hence the MM 121 should sell well and prove very popular right across the entire modelling spectrum.