I too have both. The problem with N£S cards is not a problem with the DM800 itself. The problem arrises when trying to use an N£S card in CCcam in the DM800, it simply doesn't work. If however, you were to use NewCS instead, it works just fine. So the problem is the emu not the DM. If you want Sly HD on your DM800, simply put the card in another Dreambox and share it across your lan in CCcam.
As for comparing the 2, its quite simple.
2 tuners vs 1 tuner
SD vs HD
RF output vs None.
3.5" HDD vs 2.5" HDD.
Large LCD vs Tiny OLED.
DM7025 has Compact Flash.
DM7025 has 2 card readers.
DM7025 has CI slot.
The better machine is quite clearly the DM7025. Although most people want the DM800 for the HD capabilities.
Bring on the DM8000 it will rule the entire scene !