I'll be in the minority on this, but I'd go OZ. I like their food much better than NH. I assume they still do it, but haven't checked in a while, OZ has a pre-order service with quite an extensive menu for F. I seem to remember that I had to call in to order, but it's been 3 or 4 years ago, might be online now.
Something else you might want to consider, if using UA miles for this is LH via FRA. It opens up very frequently within 2 weeks of departure, gives you 2 good length F flights and the First Class Terminal in FRA is phenomenal. I'd do that route again in a heartbeat if I had the extra time vs going direct. F seat on OZ and NH is better than LH for certain, but I loved the total experience.