Can't speak to US Envoy from personal experience, but I think they have a product worth investigating on this route.

I found Delta's recliner 'C' seat (763 B/E) to Israel slightly more comfortable than the CO's 777 angled 'lie-flat' product. Either way, a bag under the feet and a little blue pill makes the flight go by pretty quickly. The food on DL was slightly better. The price was 50% less than CO BF, making my choice pretty simple. I've seen some pretty decent fares running on both, but I'd let that drive the decision. If 'C' is only 100% more than 'Y', might be a good value.

I think if you connect through ATL, then you can have a new lie flat seat on DL.