Here are some basic questions to consider.
Is it defined contribution or defined benefit pension scheme?
If it is defined benefit, is it final salary or average earnings based?
How much does the company contribute?
How much do you contribute?
What are the management charges for administering the scheme and who pays them?
Where is the money invested?
Has the insurance company a good track record of producing returns?
If it's a defined benefit final salary scheme, snap their hand off!