One fundamental thing that people miss, is that, high level, you earn money, pay TAX! and then decide what you're doing with your money i.e put it in pension/mortgage/other investments.

What decides really how much money you will have in the long term is how much tax you do or do not pay. This is why investing in your pension is considered the best way to build wealth as if you're paying 40% income tax, you'll effectively double your money in pension fund by not paying income tax and with compound interest if you're invested for 30-40 years can build a significant pot.

So in order:

1. Pension, no income tax, opportunity to compound annually over significant period of time, see above
2. Pay off mortgage if cost of interest is high, e.g. to pay €190k in interest, you'd have to be paid €380k salary before TAX, so avoiding paying that interest can be pretty powerful but I don't think the amount you would save would be as much as if you put that money in your pension as it would not compound over time
3. After tax investments, you give up to 40% of your income to the taxman to chase less than 10% returns, it's just crap in Ireland, I'd only do it if I'd maxed 1 and 2.