Which is drangerous 250 vdc or 250 vac?

Both are equally as dangerous, as 250-volts is more than enough to exceed the .1 amp (100 milli-amps) needed to cause your heart to stop beating correctly. DC electrical current cause more sever burning than AC current does, but when the voltage is as high as 250 V, it will not matter much which type of current it is... both have the potential to kill you.