Not the easiest question in the world to answer! The 1250 is an 80 Amp air plasma.....it was discontinued by Hypertherm last year at this time......because it was replaced by the Powermax85.
The 85 is an 85 amp air plasma.....it is smaller and lighter than the 1250 (new power supply technology) it has a higher duty cycle rating......it has a higher output voltage rating (thicker cutting) and it has a new torch design (Duramax,...using a new "spring electrode" and conical flow nozzle) that will provide longer consumable life, cleaner, squarer cuts....and faster cut speeds...along with dramatically longer consumable life. There also is a better quick disconnect on the torch...making it easier to switch from hand to machine torch.....and a quick disconnect on the work ground cable. The 85 also has automatic air pressure (no setting required) as well as a digital display with diagnostic info.
You can get the same Duramax torch as an upgrade for the Powermax1250...which give you many advantages over the original torch.
So...the 1250 is a great plasma....Hypertherm's competitors were still working to catch up.....when Hypertherm introduced the 85. They are both great air plasma systems....and the price for the Powermax 1250...assuming it is in good condition...is a steal.
Oh....the new 85 will have a warranty.....
Jim Colt Hypertherm