Owning your own home

I suspect this is the wrong answer, but I would take MDF having recently had problems with pine skirting warping between purchase and installation.

I'd read this was an issue, deliberately picked the straightest pieces I could find (some were already warped) and they still ended up looking a bit crap.

That might just be B&Q though.

You won’t tell once they’re painted. Also easier to glue on. Horrible to cut though.

Raw MDF is a right ballache to paint too

MDF everywhere, especially if you can get it pre-primed. Only place we have used pine is where it hasn’t been painted or has potential to get wet, pine is a pain to use, had to reject literally half the boards we were sent.

We used MDF too, so much moisture in the plaster thought pine would warp as the plaster slowly dried out
Picked up some from Travis Perkins locally drove home with these huge bendy skirting boards wobbling on my car but they survived and happily in place now

I went for beech (oiled unpainted) myself as the floor is Beech SylvaSport, however I should have just gone for cheap B&Q stuff as none of the walls are perfectly straight and cheap skirting board would have been more visually pleasing