Toss up.
RailSounds can process multiple sound streams but only some of the sounds are available without TMCC.
TrainSounds can only process one stream at a time but you can trigger any/all with conventional control.
RailSounds allows you to have background primer mover and overlay a bell AND horn/whistle or chatter/talk. TrainSounds will suspend sound streams to accommodate most recent button push.
If you run TMCC I'd go with RS. If you run in conventional the added sounds accessible without TMCC may make TS more attractive.