Tuna hp,
Thank you for your professional, lucid, and data laden insight. In the end, macroeconomics, mission, and marketing will be the final arbiters to the customer.
Life-cycle costing is a consideration as well. I was surprised to see that the 7x only requires 0.70 maintenance hours per flight hour compared to the G550's 1.53 maintenance hours per flight hour. Engine restoration costs are budgeted at $513 per hour on the 7X vs. $622 per hour on the G550. This is on top of the leading fuel efficiency from the 7X.
All of this seems counter intuitive...you can operate three engines on less fuel, and you can complete HSI/MPI/overhaul on three P&W 307's for less than two BR 710's. Again, this data is according to Conklin & deDecker's Aircraft Cost Evaluator 2009 vol. 1.
From the operational and budgeting perspective, the 7X does have it's nose in front; but I would be happy to operate either one.