New shelving unit in living room

Any wood will be durable, you can increase durability with varnish, primer-undercoat-paint. Hardwood (oak, beech) will last longer with less prep work, soft wood (pine) will require more prep work.

Inevitably, this will be down to the finish you have. A solid wood shelving unit would need to be a hardwood and sealed or finished with a suitable durable varnish or lacquer. Of course, the most cost effective timber would be a softwood, but again, would need to be finishing with a suitable varnish or lacquer. If they’re to be painted, the most durable paint for this in my opinion would be (water based) a diamond eggshell, (oil based) durable gloss/satin wood, both dulux 😊

Any wood is good hardwood/softwood even good quality PLYWOOD or MDF . For painting/varnishing . Customer choice

It’s all according what sort of finish your after mdf is a lovely material to paint oak to varnish or stain laminate for a hard durable finish with no maintenance etc