Depending on all the usual factors:
- Cost / facilities
- Price / Frequent Flyer Miles (earn or spend)
- How many stops/changes can you take
- Do you want/need to see any one/thing along the way
- etc.
Icelandair via Keflavik - no WTP/PE but consider their Biz.
Continental Biz is highly recommended, don't know prices.
Virgin Atlantic to Chicago and then a connect of your choice (but booked all in one, of course) as that gives you PE on the long sectors.