The biggest thing is that ScanMaster works more like a 'guage' (i.e. you place it in your line of sight for instant readings). It will also store a couple of parameters max/min readings for quick tuning.
TurboLink captures all the of the data for frame by frame playback and you see all of the parameters at once on the screen.
A lot of folks use both ... ScanMaster for the "use while driving" functions and TurboLink for the "replay captured data" functions.
