So my two complete failures due to the crack were not "catastrophic" then?
The case cracking is common, and those two failures were common enough: most users would consider the phone uneconomic to fix, and not everyone has my tenacity or skill to waste time fixing their phone.
I also think it was that phone where the flash slowed enough to make it barely usable.
Back on topic.
The only Nexus I have had that hasn't had a problem was a Samsung Nexus 10 (still goes, but stuck on insecure Android 5.1).
The only Samsung phone I have had was the original Galaxy Nexus, which was still going when I gave it away last year. It's problems were: 1. screen burnin (OLED) and 2. Google didn't release Android 4.4 (due to TI dropping OMAP4 support?) even though 4.4 came out within 2 years. That phone cost more than an iPhone 4. My colleagues got iPhone 4 phones at the same time, and they got updates for twice as long and their phones remained useful for far longer.
So my experience with Samsung hardware has been good. I have always avoided buying Samsung because I hate their modified Android versions and lack of updates.
On mine the plastic frame cracked between the power button and the volume control (I think a reasonably common problem with this phone, I've never had a frame crack on any other phone). After that one button gets stuck on, which makes phone cycle reboot - OK - I can workaround that. Then the microphone went bad: that is caused by the crack causing pressure on the micro-connector which causes an electrical issue. That wasted more time and eventually my workaround for that issue failed.
I have had close experience with 5 different Nexus devices, and 4 of the 5 had nasty failure modes.
The Nexus line has been far less reliable than the iOS devices I have had experience with, and all the Apple devices got far more security updates over their useful life. Note: I usually use Android phones and iPad tablets (although I have also personally had iPhones and Android tablets).