If you've got other income so that your state pension is taxed, but you don't need the money, then if you save it in a standard savings account you'll not have recovered any of that tax, whereas putting it back into your pension fund will enable you to recover all of the tax. So against saving it directly, it would be very beneficial to reinvest in your personal pension fund instead.
Yeah I can now see it wouldn't be beneficial against deferral under that scenario though. I think it would be beneficial against deferral if you had no income and living off cash savings.
Interesting choices anyway, likely won't affect me as I'll need the money when I'm that age anyway.