I remember reading those articles. I think what it eventually came down to was iOS apps not being updated to 64-bit. I never had the white screen issues, Safari crashed every now again but not as bad as it does now (at least on my 6 Plus). I also did experience the degrade with my iPhone 5s, and it really wasn't fixed for me until I did a fresh reinstall of iOS 7.1.2.
The individual app crashing probably did have a lot to do with the 64-bit transition. But, the random resets were systemwide, and in my case, they most often occurred with the music app, which was native 64-bit. Since I don't have a 6 Plus, I can't comment on how Safari fares on that device compared to my 5s in the early stages. But, I will say that Safari was probably my most crash-prone app when running iOS 7.0 through 7.0.3. iOS 7.0.4 fixed most of the stability issues.
You might be confusing Leopard 10.5 with Snow Leopard 10.6. IMO, 10.6 was a lot larger rewrite then 10.5. Now, 10.5 did have some changes under the hood, but 10.6 had quite a few more and perfected 64-bit computing under OS X. From 10.0-10.5, the Finder was written in the Carbon API. With 10.6 the Finder was re-written in Cocoa.
No, I was actually referring to OS X Leopard 10.5. Recall that Snow Leopard was the "zero new features" update, which primarily focused on reducing the size of the OS and making the biggest push to 64-bit. 10.6 is now viewed by a lot of enthusiasts as a high watermark (I still use it on my iMac, because Lion is my EOL update and I really don't want to be stuck with that version), but it too had a ton of bugs early on.
Leopard was the big API expansion, which is similar to what iOS 8 has done. It made the OS considerably larger, and for the first time since OS X first came out, 10.5 didn't result in a significant performance improvement and made some Macs more crash-prone. It did add a lot of new capabilities that took developers time to fully implement. And that's how I see the similarities between Leopard and iOS 8 -- the benefits will develop over time as developers take fuller advantage of the new features.