Pogonation- ua only flies direct to dxb from iad.

OS C Class is better on board- catered by DO&CO whose chef is on board. Great flat bed seats (same seat as LX and SN).

As far as carriers- LX generally only releases award tickets from NA to Europe within 3 days of departure.

In terms of bed- LX=OS=AC FLAT BED. TK close but not as good as there is a middle seat. But- amazing service in C and also catered by DO&CO. LH is still converting to flat Biz.

All the European carriers will probably fly out of yyz, and lh out of yul also. Ua obv from iad-dxb which may also be a good option westward (most flights leave DXB at midnight and arrive in Europe at 6 am. Going to iad lands at 8 am and I further which gives you a full night sleep. I went dxb-zrh-USA to try swiss but the sleep I lost made it not worth it).

The departure lounges are all about the same- typical business and senator lounges. No os arrival lounge but doesn't matter since you're connecting.

Lounge in Dubai- if you're gold, senator, hon, or first class then decent lh senator lounge. Otherwise contract lounges.

For food and service: TK=OS>LX=LH>AC>UA. For details look at the trip reports forum.