Scrub brakes worked well for years. They still do. They are very dependent upon the type/style of tire they are being used with. Slicks work great. Ribbed are good. Turf savers are ok and the more agressive the tread gets they less aggressive the scrub brake becomes. Something about having some rubber to scrub against.
But, any upgrade is just that. An up grade. Exterior band brakes are probably better than most scrubs. Interior/drum brakes are better than band, etc.