While I agree with you (for the most part), I do want to say that Debian is king when it comes to upgrading across major releases. I've been using Debian since

While I agree with you (for the most part), I do want to say that Debian is king when it comes to upgrading across major releases. I've been using Debian since v1.3 and have upgraded I-don't-know-how-many machines across major versions. I've got production servers running Debian 8 right this moment that were running Debian 6 when they were installed. With regard to RHEL, I always reinstall from scratch instead of attempting upgrades. I think they're a lot better about upgrades nowadays but I still remember, very clearly, the day when attempting an upgrade was just asking for trouble.