If the X3800H has the functionality you need, then it is the better value because it has the latest features, 4 independent subouts, upgradable to DLBC, potentially even ART. That means, it can stay up-to-date for a few years, than the SR7015 that is almost outdated by now.
The SR7015 measured poorly compared to its Denon cousins, though the differences may not be audible to most people.
For Marantz, I would recommend the Cinema 40, or the 50 on a lower budget, but that's if you are in Europe or Asia (such as Singapore), where the price between M and D equivalents are not significant, in some cases, negligible (such as 0).