Your DH is right that you should seriously think carefully and crunch the numbers.
It isn’t as simple as looking at the % contribution of employer. If it were, NHS would win as they contribute over 23% to your pension.
It’s also the fact the new pension will be defined contribution and not defined benefit that you currently get. What this means is currently, your pension increase each year is defined. It is defined by your salary and service. I think NHS get 1/47 of salary added per year. So, if you earned £47k, your annual pension is growing £1k per year. This is also inflation linked and has spouse pension. It is not attached or determined by stock market performance. There is no ‘pot’ that you will need to draw down from or annuity your will have to buy to get an annual pension. It is very very good.
The private sector pension will see you and employer add to a pension pot. The value of the pot will be determined by your contributions and stock market performance. At retirement you either draw down an amount each year to live in, with the remainder invested, or you buy an annuity which is an annual pension. To get this inflation prodded or with spouse benefit, it costs more. Currently a £1k annuity costs over £35k. So if you have an £11k pension at the moment, you’d need a pension pot of close to £400k to buy that, and that’s before you add in the extra costs of inflation proofing and spouse pension.
How much you should factor this into your career planning depends on things like how many years you have remaining at work, when you hope to retire and your DH pension provision. If you only intend to work for a couple more years and your DH has a good pension (ideally DB not DC) then it won’t matter too much. Lots of people say that the ideal is to have a good DB oension and also to have some money in a DC pension as these are more flexible in terms of being able to easily take from them after 55 if you retire early, without early retirement actuarial reductions that come with DB pensions. If however, you need to work a good number of years more and especially if your DH doesn’t have great pension provision, you might really regret giving up the chance to add to your NHS pension.
We had a similar query in our family from a different public sector pension. We concluded the pay rise needed to exceed £25-30k in order to ‘break-even’ in terms of the pension hit and loss of holidays. The private sector job did pay better, but not to this level.