Powdered fillers or 2 part wood filler for skirting?

Hi it all depends on the wood mdf small pin holes either filler is fine if it's timber I'd use two pack filler ronseal as this timber is more often going to move...

"White" fillers, whether ready-mixed or powdered are not flexible, and as previously answers have said, are fine for pin holes. 2-part filler are also not flexible, although offer greater adhesive strength than "white" fillers. If you have some then this is a better choice. Ideally though, get a flexible wood filler such as Brummer or Ronseal Multi Purpose Wood Filler or Toupret Ready Mixed wood filler (my preferred choice). These should be readily available in your local decorator's merchant or DIY store. They all offer good adhesion and will flex as the timber expands or contracts.