Why are those the only choices?
At that age (especially if not yet on the housing ladder) I wouldn’t do a company share scheme if all it saved was tax/NI (I use my company’s share scheme but only because they match 1 for 1 up to 3% of salary, I used to actually sacrifice/buy 10% as was a handy way of saving without having it locked up in a pension and year or year they go up at least 8% – you do need to factor in capital gains and they’ve just cut the allowance though). If the share scheme didn’t match any then unless I was really confident they’d perform better than an investment fund I wouldn’t bother.
Investing early into a pension is always a good idea but the flipside is you’re tying up your money and for a lot of young people they have a more important need for it in the short term.
So personally I’d continue with the minimum contributions to the pension and increase savings via an investment fund, until I was on the housing ladder, had done any renovations it needed, had a car etc. and only then start paying a larger amount into my pension (which for me was in my late 20’s)