For those with knowledge of both products, I appreciate your insights:

I have the opportunity to book a 13-hour flight in either UA 777F or Air Canada 787-900 J. My primary concern is sleep comfort. I believe that the UA seat may be be a little wider and the cabin is much smaller, so less traffic. Any thoughts?

Even if you were to pick the UA as the better sleep product, how comfortable is the Air Canada J seat for sleeping?

Many thanks!