When i buy butter or margarine should i give most attention to saturated or trans fat (dieticians need not respond)?

Avoid trans fat: Recent scientific studies have showed a much stronger link between trans fats and negative health outcomes.

Trans fat: I recommend trying to steer clear of trans fat. While both saturated and trans fat can lead to increases in your LDL (bad) cholesterol, saturated fat can increase HDL (good) cholesterol. Trans fat, on the other hand, is associated with decreases in HDL. Trans fat also appears to be associated with other unfavorable effects, such as increases in inflammation processes.