To be honest it shouldn't make much difference to you now. The real difference is as you approach retirement.
If you are taking out an annuity at retirement you are effectively switching into guaranteed investments at retirement. The annuity default investment strategy reduces the risks associated with a sudden change in investments i.e. in the 5 to 10 years ahead of retirement your funds will gradually switch into guaranteed funds.
My view is that you should regularly assess the investment profile of your pension anyway, if you dn't think you'll do this then choosing a default strategy is the next best option