I'm not sure what the OP 'mergy' intended, but I'd guess that the intended reason had to do with better ecosystem curation. Under the hood, my understanding is that .rpm is marginally inferior to .dpkg, but not remarkably so. E.g. using cpio instead of gz as the format basis. So by elimination, the only reason to prefer .rpm would be the rpms, if you follow.

As a longtime Fedora user and a recent emigre (post-Snowden) to OpenSuSE, I agree that there is much to love about the selection of RPMs available, especially under Fedora. Although I'm sticking with suse for the lightning-fast zypper (still noticably faster than yum or even its slated nextgen replacement dnf!) and well-thought-out snapper utilities. But that is OT.