They are completely different systems. They run off entirely different operating systems. Each has things that the other does and doesn't offer. The TZT2 offers lower power usage, Active Captain, Sirius Audio controls (using BBWX3),and other items that the TZT doesn't have. (like built in sounder and GPS) The TZT2 offers a Rotokey control, some advanced radar features, multi-card reader etc.. to name a few. It is like asking someone what shoes should I wear. The fit is different for each customer.
As a general rule, knowing nothing else, if the boat is 35ft or under the TZT2 is normally the one to consider and TZT for larger boats. This isn't a hard and fast rule because you might have a long sail boat where the power savings of the TZT2 is the better choice. You might also have a smaller boat plans to run a CHRIP sounder and finds the Roto-knob something they wish to have because of all the pitch and roll. (Either could add remote keys MCU002/MCU004)
You will find many discussion treads already on this forum talking about the differences. So in summary, it is best to discuss your choice and shop for the best device to fit your boating needs. Trying to wear your neighbors shoes can result in sore feet.
