I have the 11 inch pro and find it perfect for sofa use. I personally would find the 12.9 inch too big for casual use. However I also have a 13 inch MacBook Air. Based on your use case I would say go with the 12.9. If it’s your only device then I think you would be better with the 12.9 inch. Why not try out the 12.9 inch first and if you find it’s too big exchange it for the 11 inch.