What's worse low blood pressure or high?

Both: Either severe drop or severe rise in blood pressure can be dangerous.

High: High blood pressure is worse. Low blood pressure in its common form (not including pots) causes dizziness when standing from a lying or sitting position. While low blood pressure can be very annoying it rarely leads to the multiple issues that high blood pressure can. For instance chronic high blood pressure thickens your heart muscle and predisposes you to having a heart attack.