Honestly, my money is on D2D. I had some issues with it in the past, but I was contacted by the assistant manager, and he was very helpful in fixing everything. The newest version through them doesn't include any tricky installs like in the past. It appears to be the contents of the DVD, which you can easily burn to a DVD as a backup.
Plus, no DVD needs to be in the drive, so you can file the DVD away somewhere until you need to re-install.
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GWX 2.0 w/ OLC GUI 1.2.3 for GWX 2.0
DiD, 79% realism (by the OLC GUI standards).
Currently taking a break from the Atlantic to hone my flight-sim skills