I recently took a pension buyout, for 2 reasons.
First, the math worked (and it was smaller with a much longer time frame than yours).
The second reason was actually emotions based; There is a risk associated with assuming that the pension plan will still be there paying out the promised benefits in X years (35! years for me). I decided that while I wasn't counting on a pension at all in my plans, the reward of guaranteed money was not worth the risk.