I have been in the CX seat, which I understand is the same as the new US Envoy Suite and the LX seat. All other things being relatively equal, I would easily choose the US Suite over LX. It simply has a more spacious feel to it than the LX seat. To me, it is one of the best business seats available; if they had UA's new C padding, there would be no contest.
I have not yet flown US Envoy, so I can comment on the service or food. I find LX service and food to be quite good, but not extraordinary by any means. I have to admit that I am almost always underwhelmed when I try carriers whose service/food/etc. is so much better than (insert name of carrier here.)
To me the trade off is the 6 AM return departure vs. several hour layover at ORD. For $300 savings, I would be inclined to take US.