I'll start & Let someone else finish. The 6t is the top of the Prizm line. It is not like the other Prizms at all. It has more features & just flat out does a better job detecting. Especially on the beach. It is built a little different than the other Prizms.it has the battery compartment where you put your arm in. Some feel that the balance is actually better even though you might be adding a couple of ounces. I just started using it when Winter set in. I really am looking forward to putting it through the paces when the glacier melts here. I had a Prizm 5, and the 6T is a much better detector in my opinion. So compared to the other Prizms the 6t is in a class all its own. Of course it costs a bunch more also. As far as comparing it to the M6 well I'll let Monte or some other M6 user answer that. I actually think Monte has answered it on another post. I will tell you that the coil situation is in the plus side for the M6. I am a Whites user and will tell you that either will get the job done. These may not be the big dogs of detectors, but you can play with the big dogs. It depends on how much you plan on detecting. If you see yourself upgrading to an MXT or DFX down the road choose the M6 because of the coils. If you want a detector that you can throw in the trunk & use a few times a year the 6t is a great choice. The specs & features are on the Whites web site.