Personally Siemens have a better sound.Which ever propulsion the R142A's have cannot handle 3rd rail gaps.They buck like a fat prostitute on top.Its like when Airline companies order a fleet of planes,the customer has a choice of engines to choose from various manufactures like GE,SNECMA,Pratt & Whittney,Rolls Royce.Im not sure if it works the same with Mass transit orders.