Many people do fall on the side of wishing they hadn't choosen the SBP after they do, but there is no right choice for everyone.

Try to figure out the expected life expectency of yourself and your spouse. Once you see your life expectency you it isn't that hard to figure out if a 15% cut in income is probably good financial decision, but still you have to ask yourself is a few more dollars now worth leaving my wife without guaranteed income? In answering this question don't forget to ask yourself how much additional savings do you have for your wife to live upon if you did pass away.

Good luck in making a good decision.