The two schemes grant relief on your contribution in completely different ways, and that's what decides which one is better for you.
My Future Fund (auto-enrolment)
Your contribution comes out of your net, post-tax pay. Instead of Income Tax relief, you get a flat State top-up of €1 for every €3 you contribute, worth roughly a third on top, regardless of your tax band.
Traditional PRSA / occupational pension
Your contribution comes out of your gross, pre-tax pay. Income Tax relief applies at your marginal rate, so a higher-rate (40%) taxpayer effectively only gives up 60c of net pay for every €1 that reaches the pension.
The practical rule of thumb: if your income sits below the €44,000 standard-rate cut-off, the two schemes land in a similar place, and the guaranteed employer match makes auto-enrolment a straightforward win. If you're a higher-rate taxpayer, a traditional PRSA or occupational pension with 40% marginal relief generally delivers more pension for the same net cost, which is worth discussing with your employer if you have the option to opt for one instead.