Helloo!
Well, for a start, there are different types of Nyatoh doors based on the carpentry works:
Nyatoh Solid Door
Nyatoh Semi-Hollow Door (Finger joints, and overall frame plus additional parts are from Nyatoh Solid Timber but the remaining are empty, hence hollow)
Nyatoh Hollow Door (Only the frame and essentials are made of the Nyatoh Solid Timber, the rest is hollow. Hence, a hollow knock sound can be heard when you knock on the door)
Nyatoh is basically a type of timber wood (light and reddish wood imported from Malaysia). Hence, when you are comparing between Nyatoh and Solid Plywood, you would need to compare between the different types of timber wood to have a fairer gauge. Solid plywood may just be plywood from different types of timber wood to make up the door, not necessarily from Nyatoh Timber wood. I hope my answer is clear enough!
I'm from U-Court Wood Products, the specialised wholesaler and supplier for Nyatoh Timber Wood, Reconstituted Veneer Plywood, Meranti Finger Joints, S4S Sawn Timber etc to businesses, merchants, retailers and carpenters. Hopefully some of the pointers are proven useful! You can also look us up at www.ucourtwood.com if you require any supply of timber wood.