the Emanage set up isnt a piggy back, per se. but its not a standalone... it uses the stock ECU for all the mundane and hard to program functions and then takes over when the ECU cant handle shit, like the option MAP sensor, the AFM correction, the Injector DC tunability, the ignition timing altering system, etc. theres datalogging and real time display, etc. its the shit, trust me.

oh yea and you can mess w/ your VTECH change overs too. its pretty cool shit.

but, im in the same boat as you are. ive never dealt w/ the Hondata or know anything about it so i couldnt really make any valid comparisons, all i can tell you is what the G-unit has.