you need to find one of those chain rings and hold it in your hand (if you're trying to decide which would be better a triple or a compact)
they weigh about the same as 3 ounces of water. I doubt that the extra weight of a triple is going to slow you down.
However, further back, i heard someone say it would be easier mechanically speaking for you to switch from what you have to a compact than it would be to a triple.