How much will you have available to save over the 10 years? Are you a basic rate tax payer?
If the DB pension income will take you over the personal tax allowance, there are three main advantages to also saving into a personal pension, but I'm not sure if a 10 year time frame would be sufficient to make it worthwhile compared to the accessibility of an ISA.
1.Access to the personal pension tax free within your personal allowance, if you plan to retire before the DB pension is due.
2.Benefits claimed due to ill health or redundancy would not count pension as savings, unlike an ISA.
3.The tax advantages.
The tax free lump sum from the personal pension. On a £20K pension you'd save about £1000 in tax in total from the lump sum if you are a basic rate tax payer.
If your DB pension was over the personal allowance, all other income from the pension would be taxed.
If you're a higher rate tax payer now you'd receive a greater uplift in the pension, and perhaps be taxed at a lower rate on retirement on the income.
A basic rate tax payer looking to save less than £20K overall, and planning to work until the DB pension kicked in, an extra £1K (or less) from the tax lump sum might not be sufficient entice you to choose the restrictions of a pension over a mixture of cash ISA and S&S ISA.
(I'm not an IFA or tax expert).