I do hate to complicate this further.
First of all, I do broadly agree with Brendan's assessment of the net of tax investment arithmetic.
You get 41% relief on the way in and pay 52% on the way out assuming current tax rates, PRSI and USC continue to apply. So to begin with tax is actually a negative - one of the great marketing gimmicks is that pension provision is heavily tax subsidised - it is true up to a point, but you seem to be beyond the point where you would be getting tax subsidised lump sums or paying tax on your marginal pension at lower than top rate.
There is of course the tax free roll up within the fund but again I find this underwhelming. The way I look at it, and I presume you are broadly free to chose your type of fund, for a proper comparison with mortgage lending you should consider a bond fund or even a cash fund. Even with no tax, after charges you'd be lucky to earn 2% p.a. so yet another reason to shun the AVC route and pay down the mortgage. Of course, with still a bit of time left to run most financial advisors would recommend investing in a managed or equity style fund. But you should note that this is essentially a gearing decision much like Endowment Mortgages and most commentators these days frown on these. So no compelling investment reason to keep making those AVCs.
But now we come to probably the most difficult aspect of the choice.
Under current pension rules, and presuming your scheme is not an exception, your AVCs must be received by way of pension - not by way of lump sum, as this is already covered. Exactly how much pension you get for your AVCs will depend on your scheme but it does generally tend to be good "actuarial" value i.e. you get a higher pension than you could buy in the market. Okay so that is one up for the AVCs but you face a very difficult what we call in the game "utility" choice, let me explain.
Let's say you are faced with a choice of 100K in your pocket at age 65 or a pension of 5k p.a. for the rest of your life. An actuary might tell you jump at the 5k p.a. But think about it, after you consider the interest you might earn on the 100k you will probably be 90 before you can sit back in your nursing home and pat yourself on the back (if you can reach) at having made a shrewd call all those 25 years ago
With the 100k in the hand of course you have so many more options, your call.
Your position is also slightly complicated by the fact that your wife is in the public service. My recollection is that they have fairly attractive AVC arrangements though again I think they come in the form of enhanced pension and so back to that utility question.