Both will work as pre-amps. The whole point behind any of those processors as they have a wealth of effects and cabinet modeling to make it so you can plug into an amp, mixer, or computer easily. I looked into the Zoom piece, and it has the same design and set-up as they have for had some time. Those very much function the same way, but I am sure they don't have all the cabinet modeling options like you have on the Digitech. Both will work, but the Digitech I am sure will sound better.

You do have multi-effects units that don't have amp modeling, which is desired in some cases but not in others. If you like the sound of your amp, than you honestly don't want the sound of amp modeling getting in the way of that. If you are running into a mixer, than yes amp modeling would be ideal.

This is my long winded way of saying that both will function for what you want, but I would recommend the Digitech.

Good luck! :eek: