Tell me if I'm wrong but my feeling is that Boeing 7E7 is a solution that takes into account the simple fact that airlines burned more cash than thez earned in the past 25 years.
After the worldwide recession (US+JAPAN+Europe), amplified by 11/9, plus SARS, plus Desert Storm, plus plus plus... I guess that airlines might rather bet on an A/C you can use in almost any circonstances instead of a mega-jumbo that will end up in the Mojave desert at the very first crisis striking again the airline business.
Both pretenders say they intend to improve the cost/revenue ratio by 20%. But where is the gain if people fear flying ? Investing less in smaller A/C that cost you less if you have to return them to the lessor means less financing requirments and less risks in case things takes again a bad turn.