Failing to investigate an enhanced annuity at retirement could be equivalent to throwing away 15 years of extra fund performance, Just Retirement claims.
Figures show the average maturity value of with-profits pensions was 56,518 over the last 15 years.
The top performing policy produced 77,130, which is 36% more than the average.
However, failing to claim an enhancement could mean that even a client in the best performing plan could end up not much better off than someone on an average fund.
Peter Ellis, head of annuities at Just Retirement, says a standard annuity as low as 4,900 per year could be bought with a fund of 77,130, according to the Financial Services Authority tables, whereas a fund of 56,518 could obtain an enhanced rate of 4,934.
The benefit of selecting a good provider pre-retirement could therefore be completely lost as it equivalent to throwing away 3.8% per year in extra performance.
On the other hand, selecting the best pension provider pre-retirement and an enhanced annuity at retirement could result in an increase of 73% in the final pension.