There was a pensions thread but the title was a little odd
There are considerations in regards mortgage vs pension that go wider than simply the basic tax position,
such as what happens if the rules change in regards pensions, they have twice in recent times (clamping down on what people could put in, and the reversing that recently)
Talk of making it taxable up front, but non taxable when paid, Gov of course like this since it pulls tax forwards
If you have high LTV you can face more issues and higher rate in regards your ongoing mortgage, plus you could in theory be in a more difficult position should the market crash
What happens if you need to take a job for less money, or you cannot work full time?
Its basically risk vs reward.
There is a mid point thats kind of balancing the risk which is to use the ISA allowance and S&S investments. Should you need the capital its at least available even should you end up having to take it when the market is on a downer (which can happen with pensions as well depending how they are invested)
Your relying on the investments generating more than your interest rate.
But its very personal and situational this stuff so you really need advice to be able to find a reasonable risk vs reward profile for you individually.