Hi, I am on my third Nexus 4 and Second Nexus 5.
One 4 developed a touchscreen dead area, another died after having a bath in the river, my first Nexus 5 got into a boot loop - I am told because the on/off micro switch failed. I purchased a new one but need a microscope to change it - they are really tiny. The battery life is much better on the 4 - but after having terrible (4 hours max) battery life on the 5 and I also noticed the phone was getting very hot I tried a launcher reset, an erase and reset - and switched on screenlock but it was to no effect. In the end a re-installation via ubports installer did the trick. I bought the Polarcell battery which now gives about 2 1/2 days on standby - happy to note also the bluetooth connection to vehicle works far better now - it used to connect and drop - but next time I must back up settings as I lost a fair amount of time setting everything up again. I am a dabbler not a typical Linux user - I generally copy and paste others scripts to try to make things work. Ubports Touch I think is great OS for phones - I had to use basic Android and found the experience frustrating. I think the lesser functionality of the 4 is acceptable when you take into account the battery life. Cheap as chips on Ebay if you are willing to wait.