new railings - should I use cedar or treated pine?
Interior? Exterior? I'll assume exterior, since you're even considering pressure-treated wood. Cedar generally stands up to weathering considerably better than untreated pine does - hence the cedar siding &amp; roofing all across the USA, but treated pine weathers reasonably well, too. It does like to split a little. Either will require careful priming with shellac before any painting... except you can't paint pressure-treated wood for about the first year after installation.

Last... this is for a working handrail? Based upon nothing other than the fact that a pressure-treated splinter in the hand is worlds away more painful than a cedar splinter in the hand, there's just no question: go with the cedar.