No doubt a good price as I stated on the other forum. But since your here on this forum I will tell you why the 250 is the better buy.
1. On the Ace 250 you have complete control over the 12 notches. You can accept or reject any or all of them.
P4 Has smart notch. This means when you go into that mode your discing out iron, foil and tabs. That's really all you can do. The P4 has 8 notch segments compared to the 12 the 250 has.
2. Batteries. The 250 runs on 4 cheap AA cells. The P4 runs on 2 expensive 9 volts. Battery life is about the same for both machines.
3. Coils. P4 has available the 8, 9 and 9.5 inch coil. You see they are really about the same size! The Ace 250 has a 4.5, 6x9 and 9x12 coil. Plus they are cheaper in price.
4. Modes. Ace 250 has 5. The P4 has one. If you set up a custom mode on the 250 it will remember it after you turn it off. The P4 forgets it.
Now Dayhut has it right. Buy the P4 and sell it. Then you'll make enough to buy a new Ace 250! Plus some accessories to boot.....