Trees are a renewable resource! It's not about how many you kill, it's about how sustainably they're grown/harvested.

Plywood uses less wood, but sticking the layers together involves glue and high heat. Also, in the US, it is almost exclusively manufactured in California, so if you're on the east coast, you have to add in shipping.

Overall locally sourced, sustainably grown solid wood is the most eco-friendly. Unfortunately it can be hard to find out this information.